Inkjet compositions and processes for stretchable substrates

ABSTRACT

Novel inkjet ink compositions for forming an image in a form of an elastic film attached to a surface of a stretchable and/or flexible substrate and processes utilizing same for inkjet printing color images on various substrates such as colored and absorptive or impregnable stretchable materials, which are characterized by heightened efficiency in process time, ink and energy consumption, as well as products having durable, wash-fast and abrasion-fast images printed thereon by the process, are disclosed. The novel ink compositions comprise a first part, which contains a property-adjusting agent and a carrier, and a second part which contains an emulsified property-sensitive proto-elastomeric film-forming agent, a colorant and a carrier, such that the second part congeals upon contact with the property-adjusting agent. The second part is digitally applied to the substrate less than 1 second following the application of the first part to the substrate.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/774,073 filed on Jan. 28, 2020, which is a continuation of U.S.patent application Ser. No. 16/558,356 filed on Sep. 3, 2019, which is acontinuation of U.S. patent application Ser. No. 15/424,943 filed onFeb. 6, 2017, now U.S. Pat. No. 10,472,533, which is a continuation ofU.S. patent application Ser. No. 13/975,399 filed on Aug. 26, 2013, nowU.S. Pat. No. 9,611,401, which is a continuation of U.S. patentapplication Ser. No. 12/853,389 filed on Aug. 10, 2010, now U.S. Pat.No. 8,540,358, which claims the benefit of priority under 35 USC 119(e)of U.S. Provisional Patent Application Nos. 61/272,436 and 61/245,333,both filed on Sep. 24, 2009, and of 61/232,494 filed on Aug. 10, 2009.

The contents of the above applications are hereby incorporated byreference as if fully set forth herein.

FIELD AND BACKGROUND OF THE INVENTION

The present invention, in some embodiments thereof, relates to inkjetprinting techniques and, more particularly, but not exclusively, toimproved processes and compositions for inkjet printing of highresolution color images on stretchable and/or flexible absorptive andnon-absorptive substrates of all colors.

The ever growing market of printing complex designs and images on almostevery type of surface, and especially on knitted, woven and non-woventextile surfaces, plasticized and laminated fabrics (soft signage) andthe likes, creates demands for new and more versatile printingtechnologies and materials. One such demand is for ink compositions andtechnologies which will be suitable for printing long lasting, durable,abrasion resistant, water-, detergent- and chemical-fast color images ona variety of materials, which will not wear out rapidly upon use,handling, washing and exposure to the environment. The garment industryis possibly the most demanding in terms of printing high quality anddurable prints of textile, adding some requirements from the product,such as pleasant hand-feel of the printed area, flexible (bendablewithout cracking), stretchable and aerated print area, as well asfollowing the guidelines of internationally accepted standards such asthe Oeko-Tex Standard 100 (an international testing and certificationsystem for textiles, limiting the use of certain chemicals, which wasdeveloped in 1992) and GOTS (Global Organic Textile Standard).

One of the most promising technologies for printing high quality colorimages, particularly in small batches of varying contents (short runs ofvariable data), on a wide variety of types and shapes of substrates,such as textile surfaces, is inkjet printing. Inkjet printing is awide-spread technique in which a stream of a specific liquid inkcomposition is ejected as droplets from a cluster of minute nozzles(printheads) in response to electrical signals generated by amicroprocessor to record characters and patterns on the surface of aprinting subject without making direct contact between the inkapplication apparatus and the surface of the subject (non-impactprinting). A typical inkjet printing system includes methods andapparatus in which electric signals are converted to mechanical signalsfor a continuous or on-demand jetting of an ink composition which iscontinuously supplied and stored in a nozzle head portion, to therebyrecord characters, symbols and patterns on the surface of a subject.

Reviews of various aspects of inkjet printing can be found inpublications such as Kuhn et al., Scientific American, April, 1979,162-178; Keeling, Phys. Technol., 12(5), 196-203 (1981); U.S. Pat. Nos.3,060,429, 3,298,030, 3,373,437, 3,416,153, 3,673,601, 4,312,007 and4,380,770; and numerous other publications.

The presently available ink compositions, including compositions thatare suitable for inkjet printing, include aqueous-based ink compositionsand non-aqueous solvent-based ink compositions. The more commonly usedinkjet compositions are aqueous-based ink compositions, which typicallyinclude water and a colorant, usually a dye or pigment dispersion, andmay further contain a number of additives for imparting certainattributes to the ink as it is being applied (jetted), e.g., improvedstability and flow, anti-corrosiveness, and feather and bleedingresistance), as well as attributes to affect its final cured propertiessuch as the capability to form chemical bonds with the substrate,improved adhesion to the substrate, flexibility, stretchability,softness and the like.

One of the challenges in printing on fabric is its absorbability, whichis far more challenging than that of, for example, paper ornon-adsorbent substrates.

To ensure high quality images by inkjet, the ink composition should becharacterized by free passage through the nozzles, minimal bleeding,paddling and/or smearing, uniform printing on the surface of thesubject, wash-fastness, simple system cleaning and other chemical andphysical characteristics. To meet these requirements, the inkcomposition should be characterized, for example, by suitable viscosity,solubility, volatility, surface tension, compatibility with othercomponents of the printing system and, in cases of continuous flowinkjet printing, electrical resistance, and further be applied usingsuitable apparati, techniques and processes.

In case of printed fabrics (e.g., printed garments), in order to sustainwear and tear due to frequent use and wash cycles, the printed image onthe final product, as well as the final product itself, should exhibitthe properties of an elastic yet aerated film, and therefore the inkcomposition should also contain components which can impart suchcompressibility (softness), plasticity, elasticity, flexibility andstretchability.

During the last decades, numerous techniques, compositions and apparatifor inkjet printing in general, and particularly on textile andgarments, have been developed. See, for example, U.S. Patent ApplicationNos. 2002/0022120, 2002/0060728, 2003/0142167, 2003/0157304 and2005/0098054 and U.S. Pat. Nos. 4,702,742, 5,349,021, 5,594,044,5,645,888, 5,988,791, 6,042,228, 6,117,921, 6,126,281, 6,140,391,6,322,620, 6,326,419, 6,341,856, 6,513,924, 6,536,894, 6,606,427,6,626,530 and 6,879,378.

U.S. Pat. Nos. 6,196,674 and 6,500,880 and U.S. Patent Application Nos.20010008908 and 20010018472 teach inkjet compositions which are said toalleviate feathering and bleeding problems of inkjet printing onsemi-absorptive substrates, mainly paper and stationeries which are notdesigned or expected to bend or stretch.

Typically the thickness and the absorbance in the vertical direction(depth), as oppose to its surface in the XY field or horizontaldirection, of any untreated fabric, are many orders of magnitude higheras that of paper, and particularly when compared to inkjet paper media,which is pre-treated to exhibit specific ink-retention and absorptionproperties. While contemporary inkjet paper media is designed for inkjetprint and therefore supplied after being pretreated to retain the liquidinkjet, for example, by coating the surface of the paper with fumedsilica and alike. Typical textile pieces are not intended for digitalprint application and therefore must be either pretreated “off-line”prior to the printing process.

IL Patent No. 162231 and WO 2005/115089 by the present assignee, whichare hereby incorporated by reference as if fully set forth herein, teachprocesses and systems for printing high quality, high resolution,multi-color images on fibrous or porous materials or other ink absorbingmaterials, or on materials having high surface tension with the inkliquid, and especially over garments, effected by applying a wettingcomposition prior to applying an ink composition and formation of theimages. Specifically, the process of printing an image on a surface iseffected by contacting at least a part of the surface, preferablycovering slightly more than the area which is intended for the image,with a wetting composition so as to wet that part of the surface. Thewetting composition is capable of interfering with the engagement of aliquid ink composition with material, such that when applying the liquidink composition on the wetted surface, the ink is kept from smearing andabsorbing in the material, allowing to form a high-quality image on thewet part of the absorptive surface. According to some embodimentsdisclosed in IL Patent No. 162231 and WO 2005/115089, the wettingsolution is applied in a way so as to soak the textile media therewith.

IL Patent No. 162231, WO 2005/115089 and U.S. Patent Application Nos.20070103528 and 20070104899, by present assignee, therefore teachmethodologies involving pre-treatment of textile pieces which are wetted“on the fly”.

U.S. Pat. No. 7,134,749 by the present assignee, which is herebyincorporated by reference as if fully set forth herein, teaches a methodand apparatus for color printing on a dark textile piece. According tothe teachings of this patent, the method includes the steps of digitallyapplying a white opaque ink layer directly onto a dark textile piece,and digitally printing a colored image on the white ink layer.Specifically, the method for color printing on a dark textile piece iseffected by digitally printing, by means of an inkjet printing head, anopaque white ink layer directly onto a dark textile piece; and digitallyprinting a colored image on the white ink layer. The digital printing ofthe white ink layer is performed such that the white ink layersubstantially covers, without exceeding, the designed area of thecolored image, and further such that the white ink layer and the coloredimage are substantially coextensive.

U.S. Patent Application Nos. 20070103528 and 20070104899, by the presentassignee, which are hereby incorporated by reference as if fully setforth herein, teach individual and integrated processes, methods andcompositions for printing high quality, high resolution, multi-colorimages on lightly and/or darkly colored fibrous or porous materials orother ink absorbing materials, which also provide a mechanism for dropimmobilization aimed at inhibiting the adsorption by fabric, thebleeding, smearing, paddling and feathering of the jetted ink droplets.These integrated processes are effected by digitally printing a layer ofan opaque, lightly colored ink composition, followed by digitallyprinting the colored image thereon, and optionally further involveapplying a wetting composition prior to and/or subsequent to printing ofthese layers. These documents further provide multi-componentcompositions and processes utilizing wetting compositions and/ortwo-part liquid ink compositions which can interact therebetween asproperty-adjusting and property-sensitive pairs, so as to effect achemical and/or physical change in one or more of these parts, and thusobtain improved binding and color perception of the resulting images onsurfaces, particularly in cases of absorptive substrates.

SUMMARY OF THE INVENTION

The present inventors have now designed and successfully practiced novelprocesses for printing high-quality and physically durable andserviceable color images on various surfaces, including absorptive andnon-absorptive substrates, which are especially suitable for inkjetprinting on stretchable, flexible and bendable materials, and utilizeinter-reactive agents which are capable of interacting upon contacttherebetween on the surface of the substrate so as to effectimmobilization of the liquid ink composition. To this effect, thepresent inventors have designed and successfully practiced, novel inkcompositions, which are suitable for use in these and other inkjetprinting processes.

The novel ink compositions disclosed herein are intended to produce insitu, during the printing process, an image which is formed from two ormore separate and discrete parts, or components, of the ink composition,each of which is jetted or sprayed onto the surface of the substratefrom a separate and discrete printhead or nozzle. Some of these partsare jetted by a digitally controlled process, while some may be sprayedby a less precise and repetitive manner. These components must be keptseparately until used in the printing process since they are reactivetherebetween. Once in contact therebetween on the surface of thesubstrate, the various components of the liquid ink composition are notabsorbed into the substrate, as a result of the aforementionedreactivity which effects congelation of the composition upon formation,an effect which is referred to herein as immobilization. Thus, thecongealed composition droplet is less fluid and hence less mobile andless free to wick into or spread over the substrate. The variouscomponents of the liquid ink composition are not absorbed into thesubstrate also as a result of particular printing process parameters,such as minimal time interval between the application of each component,and a small average volume of the jetted droplets while being applied onthe substrate. Once the printing process is over in terms of applyingthe ink composition on the substrate, the composition undergoes curingwhich transforms it into a film which is durable and elastic, andaffixed firmly to the substrate.

Thus, according to one aspect of embodiments of the present inventionthere is provided a proto-elastomeric film-forming inkjet compositionwhich includes a first part and a second part, wherein the first partcomprises a property-adjusting agent and a first carrier, and the secondpart comprises an emulsified property-sensitive proto-elastomericfilm-forming agent, a colorant and a second carrier, whereas the secondpart congeals upon contact with the property-adjusting agent, the inkjetcomposition being for forming an image in a form of an elastic filmattached to a surface of a stretchable and/or flexible substrate.

According to some embodiments of the invention, the second part furthercomprises a first metal oxide.

According to some embodiments of the invention, the first metal oxide issubstantially transparent.

According to some embodiments of the invention, the composition furtherincludes a third part, the third part includes the emulsifiedproperty-sensitive proto-elastomeric film-forming agent, a second metaloxide and a third carrier.

According to some embodiments of the invention, the composition furtherincludes a fourth part, the fourth part includes the emulsifiedproperty-sensitive proto-elastomeric film-forming agent, a second metaloxide a colorant and a fourth carrier.

According to some embodiments of the invention, the second metal oxideis substantially opaque white.

According to some embodiments of the invention, a film formed by theproperty-sensitive proto-elastomeric film-forming agent is characterizedby a glass transition temperature (Tg) that ranges from −35° C. to 0° C.

According to some embodiments of the invention, the first carrier, thesecond carrier, the third carrier if present and the fourth carrier ifpresent are each independently selected from the group consisting of anaqueous carrier and a non-aqueous carrier.

According to some embodiments of the invention, each of the firstcarrier, the second carrier, the third carrier if present and the fourthcarrier if present is an aqueous carrier.

According to some embodiments of the invention, the property is achemical and/or physical property selected from the group consisting ofacidity (pH), metal atom complexation, ionic strength, solubility,dispersibility, dispensability, hydrophobicity and electric charge.

According to some embodiments of the invention, the property-adjustingagent is selected from the group consisting of an acid, a base, a salt,a metal oxide, an organic solvent, a polymerization catalyst, a chargedpolymer, an oxidizing agent, a reducing agent, a radical-producing agentand a crosslinking agent.

According to some embodiments of the invention, the property is acidity(pH).

According to some embodiments of the invention, a pH of the first partranges from 3.5 to 5.5.

According to some embodiments of the invention, the property-adjustingagent is an organic acid.

According to some embodiments of the invention, the acid is a transitoryorganic acid.

According to some embodiments of the invention, the transitory organicacid is lactic acid.

According to some embodiments of the invention, the transitory organicacid is glycolic acid.

According to some embodiments of the invention, the property is metalatom complexation.

According to some embodiments of the invention, the property-adjustingagent is a third metal oxide.

According to some embodiments of the invention, the property-sensitiveproto-elastomeric film-forming agent is selected from the groupconsisting of an alkyl-acrylic polymer, acrylic-styrene copolymer, analkyl-acrylic copolymer and, an emulsified urethane polymer.

According to some embodiments of the invention, the property-sensitiveproto-elastomeric film-forming agent is a self-crosslinkingalkyl-acrylic copolymer.

According to some embodiments of the invention, the self-crosslinkingalkyl-acrylic copolymer is an ethyl-acrylic/butyl-acrylic copolymer.

According to some embodiments of the invention, the first part furtherincludes at least one agent selected from the group consisting of abinder, a film-forming binder, a polymerization catalyst, a crosslinkingagent, an amine stabilizer, an alcohol stabilizer, asoftener/plasticizer, a surface active agent, a surface tensionmodifying agent, a viscosity modifying agent, a thickener agent, ananticorrosion agent and any combination thereof.

According to some embodiments of the invention, each of the second part,the third part if present and the fourth part if present furtherincludes independently a crosslinking agent.

According to some embodiments of the invention, the crosslinking agentis a formaldehyde-free crosslinking agent.

According to some embodiments of the invention, the formaldehyde-freecrosslinking agent is selected from the group consisting of apolyaldehyde, a heteroaryl polycarbamate, a diacetoneacrylamide/hydrazine and a carbodiimide.

According to some embodiments of the invention, the first part includesa transitory organic acid or a first metal oxide and water, and thesecond part includes an emulsion of a pH-sensitive and/or metaloxide-sensitive proto-elastomeric film-forming alkyl-acrylic copolymer,a colorant and water, whereas the second part congeals upon contact withthe acid or the first metal oxide.

According to another aspect of embodiments of the present inventionthere is provided a process of printing an image on a stretchable and/orflexible substrate, the process is effected by digitally applying, bymeans of a plurality of inkjet printheads, onto at least a portion of asurface of the substrate, the proto-elastomeric film-forming inkcomposition according to some embodiments of the present invention,wherein the first part is applied by at least one first printhead of theplurality of inkjet printheads and the second part is applied by atleast one second printhead of the plurality of inkjet printheads,thereby forming the image in a form of an elastic film attached to asurface of the substrate.

According to some embodiments of the invention, a time interval betweenan application of the first part of the ink composition and anapplication of the second part of the ink composition is less than 1second.

According to some embodiments of the invention, the substrate isselected from the group consisting of an absorptive substrate and anon-absorptive substrate.

According to some embodiments of the invention, the absorptive substrateis selected from the group consisting of a knitted fabric, a woventextile fabric, a non-woven textile fabric, a cloth, a garment, paper,cardboard, and any combination thereof.

According to some embodiments of the invention, the process furtherincludes, prior to digitally applying the ink composition, flatteningprotruding fibers if present in the substrate.

According to some embodiments of the invention, flattening protrudingfibers is effected by:

a. wetting the surface by means of a wetting unit; and

b. exerting a flattening pressure on the surface after the wetting bymeans of a flattening unit head for exerting pressure on the surface.

According to some embodiments of the invention, the non-absorptivesubstrate is selected from the group consisting of a soft signage media,plastic, metal foil and any combination thereof.

According to some embodiments of the invention, the surface issubstantially a dark surface.

According to some embodiments of the invention, the average jetted dropvolume of each of the first part, the second part and the third part, ifpresent, of the ink composition ranges independently from 40 pico literto 90 pico liter.

According to some embodiments of the invention, the amount jetted of thefirst part ranges from 0.005 grams per square inch to about 0.040 gramsper square inch.

According to some embodiments of the invention, the amount jetted of thesecond part ranges from 0.015 grams per square inch to about 0.085 gramsper square inch.

According to some embodiments of the invention, the amount jetted of thethird part, if present, ranges from 0.07 grams per square inch to about0.15 grams per square inch.

According to some embodiments of the invention, the time intervalbetween an application of the first part and an application of thesecond part, and a time interval between an application of the firstpart and an application of the third part, if present, are each lessthan 1 second.

According to some embodiments of the invention, the time intervalbetween an application of the first part and an application of thesecond part, and the time interval between an application of the firstpart and an application of the third part, if present, are each lessthan 0.75 seconds.

According to some embodiments of the invention, the time intervalbetween an application of the first part and an application of thesecond part, and the time interval between an application of the firstpart and an application of the third part, if present, are each lessthan 0.5 seconds.

According to some embodiments of the invention, the film formed by theproto-elastomeric film-forming agent is characterized by a glasstransition temperature (Tg) that ranges from −35° C. to 0° C.

As used herein the term “about” refers to ±10%.

The terms “comprises”, “comprising”, “includes”, “including”, “having”and their conjugates mean “including but not limited to”.

The term “consisting of” means “including and limited to”.

The term “consisting essentially of” means that the composition, methodor structure may include additional ingredients, steps and/or parts, butonly if the additional ingredients, steps and/or parts do not materiallyalter the basic and novel characteristics of the claimed composition,method or structure.

As used herein, the phrase “substantially devoid of” a certain substancerefers to a composition that is totally devoid of this substance orincludes no more than 0.1 weight percent of the substance.

The word “exemplary” is used herein to mean “serving as an example,instance or illustration”. Any embodiment described as “exemplary” isnot necessarily to be construed as preferred or advantageous over otherembodiments and/or to exclude the incorporation of features from otherembodiments.

The words “optionally” or “alternatively” are used herein to mean “isprovided in some embodiments and not provided in other embodiments”. Anyparticular embodiment of the invention may include a plurality of“optional” features unless such features conflict.

As used herein, the singular form “a”, “an” and “the” include pluralreferences unless the context clearly dictates otherwise. For example,the term “a compound” or “at least one compound” may include a pluralityof compounds, including mixtures thereof.

Throughout this application, various embodiments of this invention maybe presented in a range format. It should be understood that thedescription in range format is merely for convenience and brevity andshould not be construed as an inflexible limitation on the scope of theinvention. Accordingly, the description of a range should be consideredto have specifically disclosed all the possible subranges as well asindividual numerical values within that range. For example, descriptionof a range such as from 1 to 6 should be considered to have specificallydisclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numberswithin that range, for example, 1, 2, 3, 4, 5, and 6. This appliesregardless of the breadth of the range.

Whenever a numerical range is indicated herein, it is meant to includeany cited numeral (fractional or integral) within the indicated range.The phrases “ranging/ranges between” a first indicate number and asecond indicate number and “ranging/ranges from” a first indicate number“to” a second indicate number are used herein interchangeably and aremeant to include the first and second indicated numbers and all thefractional and integral numerals therebetween.

As used herein the term “method” refers to manners, means, techniquesand procedures for accomplishing a given task including, but not limitedto, those manners, means, techniques and procedures either known to, orreadily developed from known manners, means, techniques and proceduresby practitioners of the chemical, pharmacological, biological,biochemical and medical arts.

Unless otherwise defined, all technical and/or scientific terms usedherein have the same meaning as commonly understood by one of ordinaryskill in the art to which the invention pertains. Although methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of embodiments of the invention, exemplarymethods and/or materials are described below. In case of conflict, thepatent specification, including definitions, will control. In addition,the materials, methods, and examples are illustrative only and are notintended to be necessarily limiting.

It is expected that during the life of a patent maturing from thisapplication many relevant methods, uses and compositions will bedeveloped and the scope of the terms methods, uses, compositions andpolymers are intended to include all such new technologies a priori.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

Some embodiments of the invention are herein described, by way ofexample only, with reference to the accompanying drawings. With specificreference now to the drawings in detail, it is stressed that theparticulars shown are by way of example and for purposes of illustrativediscussion of embodiments of the invention. In this regard, thedescription taken with the drawings makes apparent to those skilled inthe art how embodiments of the invention may be practiced.

In the drawings:

FIG. 1 presents a schematic diagram illustrating a digital printingmachine with a wetting unit, a flattening unit and a printing head,according to a first embodiment of the present invention;

FIGS. 2A-2B present schematic diagrams of an exemplary printing machinewith a roller-flattening unit according to a further embodiment of thepresent invention (FIG. 2A), and an exemplary printing machine with acurtain-flattening unit, according to a further embodiment of thepresent invention (FIG. 2B);

FIG. 3 presents a schematic diagram of an exemplary carousel-printingmachine using a flattening unit according to an embodiment of thepresent invention;

FIG. 4 presents a schematic diagram of an exemplary matrix-printingmachine using a flattening unit, according to an embodiment of thepresent invention;

FIG. 5 presents a schematic diagram from the side, of a printing machinecomprising a wetting unit, a roller type flattening unit and a printingunit;

FIG. 6 presents a simplified flow chart describing an exemplary printingprocedure for printing on a dark garment using a digital printingmachine with a flattening unit according to an embodiment of the presentinvention;

FIG. 7 presents a schematic side view of a digital printing machinecomprising an exemplary flattening unit in operative state;

FIG. 8 presents a schematic side view of an exemplary digital printingmachine comprising an exemplary flattening unit in non-operating state;

FIG. 9 presents a schematic view of an exemplary flattening unit inoperative state;

FIG. 10 presents a schematic view of an exemplary flattening unit innon-operative state;

FIG. 11 presents a close up view of an exemplary digital printingmachine comprising an exemplary flattening unit in operative state;

FIGS. 12A-12C present color photographs of three untreated black 100%cotton textile pieces having an opaque white part of an ink compositionapplied thereon by an inkjet printer, comprising opaque white titania asa pigment and as a metal oxide, and an acrylic emulsion as aproperty-sensitive proto-elastomeric film-forming agent emulsified indeionized water, printed in a pattern of about 65 mm stripes at apre-designed drop-density levels, wherein FIG. 12A shows the results ofprinting the white part of the ink composition printed without anyattempt to immobilize the ink before curing, FIG. 12B shows the resultsof printing the white part of the ink composition printed after sprayingthe cloth with a wetting composition (as disclosed in WO 2005/115089),and FIG. 12C shows the results of printing the ink composition, using aprocess according to embodiments of the present invention, as a firstpart (the immobilization part), which includes a transitory acid as aproperty-adjusting agent and other ingredients, together with an opaquewhite part (the third part) applied concomitantly therewith,demonstrating the inability to obtain reasonable results of inkjetprinting without immobilizing the white layer on the garment prior tocuring, the results obtained using a wetting composition, and the superbresults obtained when using the process presented herein by an exemplaryembodiment thereof;

FIGS. 13A-13B present color photographs of two untreated black 100%cotton textile pieces having colored (cyan, magenta, yellow and black,or CMYK pigments) ink compositions printed thereon in a pattern ofsquares, each square in a different combination of CMYK pigments(column-wise) and different drop-density (row-wise), printed on a whiteunderbase, wherein FIG. 13A shows the results when the colored pigmentsare printed on a layer of white underbase after spraying the cloth witha wetting composition (as disclosed in WO 2005/115089), and FIG. 13Bshows the results obtained when using a process according to embodimentsof the present invention, where an immobilization part (first part) isprinted concomitantly with the part containing the colored pigments(second part), and less than a second after an immobilization part(first part) was applied concomitantly with an opaque white part (thirdpart) using a third of the amount of white underbase (0.11 grams persquare inch) to accomplish the acceptable results, demonstrating thesuperb results obtained when using the inkjet printing process accordingto some embodiments of the present invention;

FIGS. 14A-14C present color photographs of three untreated white 100%cotton textile pieces having colored pattern as shown in FIG. 13 printedthereon, wherein FIG. 14A shows the results when the colored pigmentsare printed on the white cloth without any attempt to immobilize the inkbefore curing, FIG. 14B shows the results when the colored pigments areprinted after spraying the cloth with a wetting composition (asdisclosed in WO 2005/115089) based on 2% acetic acid and 0.1% wettingagent (BYK 348) in tap water, and FIG. 14C shows the results obtain whenusing a process according to embodiments of the present invention, wherean immobilization part (first part) is printed concomitantly with thepart containing the colored pigments (second part), demonstrating thesuperb results obtained when using the inkjet printing process accordingto some embodiments of the present invention;

FIGS. 15A-15C present color photographs of three white synthetic piecesthat serve as media for soft signage, having a colored image of apattern (as shown in FIG. 13 hereinabove) printed thereon, wherein FIG.15A shows the color image printed without any attempt to immobilize theink before curing, FIG. 15B shows the color image printed after sprayingthe cloth with a wetting composition (as disclosed in WO 2005/115089)based on 2% acetic acid and 0.1% wetting agent (BYK 348) in tap water,and FIG. 15C shows the color image obtained when using a process aspresented herein, wherein the first part (the immobilization part) isapplied concomitantly with the second part (colored part), demonstratingthe superb results obtained when using the inkjet printing processaccording to some embodiments of the present invention;

FIGS. 16A-16B present color photographs of one color image printed on ahighly stretchable black fabric (Lycra™), which was printed using anexemplary ink composition based on proto-elastomeric film-forming agentshaving Tg lower than 0° C., printed using an exemplary process,according to embodiments of the present invention, wherein FIG. 16Ashows the image on the relaxed fabric which spans about 6 cm, and FIG.16B shows the same image in the same piece of fabric, stretched to about10.5 cm without causing any degradation to the appearance of the imagedue to stretching; and

FIGS. 17A-17B present color photographs of two similar color imagesprinted on a highly stretchable black fabric (Lycra™), which wereprinted using an ink composition with film-forming agents having Tghigher than 85° C., printed by an exemplary process according toembodiments of the present invention, wherein FIG. 17A shows a similarimage as presented in FIG. 16 on the same type of fabric as shown inFIG. 16, stretched to about 10.5 cm, showing the cracks and the damagingeffect of stretching the non-elastic image, and FIG. 17B where anotherimage was printed with an extended opaque white underbase, showing thecracks and extensive degradation of the image due to stretching, ascompared to the stretched image in FIG. 16B.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

The present invention, in some embodiments thereof, relates to inkjetprinting and, more particularly, but not exclusively, to improvedcompositions and processes of inkjet printing of high resolution colorimages on stretchable and flexible absorptive and non-absorptivesubstrates of all colors.

The principles and operation of the present invention may be betterunderstood with reference to the figures and accompanying descriptions.

Before explaining at least one embodiment of the invention in detail, itis to be understood that the invention is not necessarily limited in itsapplication to the details set fourth in the following description orexemplified by the Examples. The invention is capable of otherembodiments or of being practiced or carried out in various ways.

As discussed in detail hereinabove, there is an ever-growing need formethods and compositions for improved performance of inkjettechnologies, particularly on challenging substrates such as colored(non-white) highly absorptive materials, including knitted, woven orunwoven, textile and garments that are designed and expected to stretchand laundered regularly, as well as on non-woven fabrics, soft signageand other substrates which are substantially non-absorptive materialswhich are designed to bend and flex. Such non-absorptive materialsrequire laborious pretreatment procedures which cannot be effected onthe fly during the printing process, and are not suitable for some ofthe aforementioned art of pre-treatment, wetting and printing methods,or ink compositions. Similar limitations exist in the wide and largeformat roll to roll printed fabrics. It is therefore the reason why theteachings of documents such as, for example, U.S. Pat. Nos. 6,196,674and 6,500,880 and U.S. Patent Application Nos. 20010008908 and20010018472, cannot be applied for stretchable substrates.

Some of the problems of printing on absorptive surfaces can be mitigatedby permanently augmenting the properties of the media, as in the case ofhigh-quality paper for color inkjet prints, which is essentiallypre-treated in order to optimize its liquid ink retention properties andits whiteness (enhancing its light reflectance). However, suchaugmentation of the physical and chemical properties of flexible andstretchable non-white media may be impractical to apply off-line (beforethe printing process), namely the pre-treatment step renders the entireprocess a cost-ineffective part of the technique, particularly in casesof printing on stretchable and flexible absorptive and/or coloredmaterials, such as textile. Furthermore, in cases of fabrics andgarments, whose absorption depth, contrary to paper, is many orders ofmagnitude greater, such pre-treatments may prove ineffective anddestructive to the media.

Modern research and development in the field of inkjet printing is aimedmostly at improving the ability to form a high-resolution color imageson absorptive and non-adsorptive substrates at low costs ofenvironmental implications, time, equipment and chemicals, which willstill be characterized by improved color-space coverage (color-depth),and still possess the physical properties which are required from thefinished printed image, namely the durability, flexibility,stretchability, fastness, pleasant hand-feel and breathability of theprinted area and also be acceptable under the “Oeko-Tex Standard 100”and other regulatory requirements. For example, one of the standardsrequired in modern garment and textile products is the absence offormaldehyde and phenol derivatives as well as other components that arenot suitable for direct contact with skin, and hence the inks utilizedin the production of such printed products must be free of any suchharmful chemicals.

Some improvements of color inkjet printing on textile have beendisclosed by the present assignee, as discussed hereinabove, and includewetting the garment on-the-fly with a layer of a wetting compositionbefore applying the layers of colored inks thereon, which can becombined with applying a layer of a white and opaque layer on thegarment so as to improve the light reflectance of the surface, andfurther combined with the use of multifunctional and multi-componentcompositions that can effect a chemical and/or physical change in thecombined inkjet liquid ink composition so as to limit or abolishpre-curing absorption of the ink droplets. Thus, the wetting compositionand the multi-component compositions are all aimed at causing the jettedink droplets to stay on-top and affixed to the surface of the materialwithout extensive absorption, smearing and bleeding before they dry andcure.

While practicing the above-described methodologies, the presentinventors have recognized that in order to further obviate the obstaclesposed by printing on absorptive substrates, one should consider thefactors which govern the absorption of the liquid inks into thesubstrate, mostly due to intrinsic surface tension of the materials, andthe capillary action, also known as wicking, which stem therefrom. Asthe amount of ink delivered by a printhead is typically very small, thepresent inventors have recognized that the jetted droplet must be keptas visible as possible on the substrate.

On the other hand, the present inventors have recognized that when thesubstrate is completely non-absorptive (impregnable, non-permeable),such as high surface tension and impervious substrates that do notinteract with a liquid ink composition so as to restrict the movement ofthe jetted droplets, the liquid ink droplets may sputter, spread andsmear, and droplets of different colors may flow into one another andthus greatly reduce the quality of the resulting image. In addition, thepresent inventors have recognized that the high surface tension of somenon-absorptive substrates may cause de-wetting of the surface by theink, thus preventing the formation of continuous covered areas as theink droplets tend to coalesce, leaving uncoated areas. Hence, thepresent inventors have recognized that instant immobilization of the inkdroplets on the surface of such substrate will prevent this phenomenonfrom occurring. Thus, the present inventors have recognized that factorswhich govern the localization and confinement of the liquid ink dropletson top of impregnable substrates, such as surface tension, texture(grain) and the imperviousness of the materials, should be consideredand mitigated as well the requirement for flexible and sustainableprint-work.

The present inventors envisioned that utilizing a multi-component(having multiple parts, also referred to as multi-part) ink compositionwhich comprises an immobilization part and one or more coloring partsthat are immobilized by the immobilization part, while controlling andminimizing the time which passes between applying the various parts ofthe multi-component ink composition, the capillary action can bemitigated so as to minimize and substantially eliminate the undesirableabsorption of the ink into the substrate. The present inventors havefurther envisioned that selecting suitable printheads so as to controlthe size of the jetted droplets of each part and using each partsparingly, bleeding of droplets one into another would be minimized oreliminated, affording a high-quality color image on such substrates. Theaforementioned phenomenon of intermixing of different colored dropletsapplied on non-absorptive substrates can also be mitigated or abrogatedby an almost instantaneous immobilization of the colored ink droplets.

Furthermore, the present inventors have envisioned that thisinstantaneous immobilization of inkjet compositions on absorptive andnon-absorptive substrates can be utilized on stretchable and flexiblemedia by the selection of particular formulations for the multi-partsink composition, such that will enable the formation of a stretchable,soft and flexible color prints that would not crack, flake or peel-off.

As known in the art, some inkjet compositions designed for paper andother non-stretchable substrates are based on dispersed pigmentcolorants, wherein the dispersants are sensitive to the intrinsic oradded acidity of the substrate, hence cause dispersing agents of thepigments to stop acting as dispersants, thereby lowering the flowabilityof the pigment. These systems are designed to attenuate the capacity ofthe pigments in these ink compositions to bleed into the substrate. Suchink compositions are disclosed, for example, in U.S. Pat. Nos. 6,196,674and 6,500,880.

While reducing the present invention to practice, the present inventorshave surprisingly found that emulsions of some acrylic polymers andcopolymers, which are used as binders to treat knitted, woven andnon-woven textile, break when exposed to acidity in the presence of somemetal oxides, or break when exposed to other metal oxides even withoutlowering the pH of the medium. Such acrylic polymers can be selected tohave useful cloth binding properties and form elastic films on textileand other stretchable substrates even after drying and curing.

While further reducing the present invention to practice, the presentinventors have formulated several ink compositions, which are intendedspecifically for printing color images on stretchable and flexibleabsorptive substrates such as woven and non-woven fabrics, as well as onstretchable and flexible non-absorptive (impervious) substrates, andwhich, when utilized in inkjet printing processes, produce durable colorimages that exhibit resistance to water and other chemicals, as well asto stretching and flexing, and yet are of high-quality in terms ofresolution and color-depth and have a pleasant/soft hand-feel. Theseformulations may further employ the optional use of substances that canflatten the protruding fibers of fabrics so as to afford sharper images.

The processes and compositions provided herein are designed to produceuncompromising high-quality color images on all sorts of substrates, andparticularly on some of the most challenging substrates for inkjettechnology in the industry, namely substrates which are not kept flat,dry and relaxed, but rather used in a variety of environments, chemicalconditions and physical impact. Such substrates are stretchable andflexible in all directions to some extent, and therefore any imageprinted thereon must also be co-stretchable and co-flexible to the sameextent with the substrate, as can be achieved according to theembodiments provided in the present invention.

Thus, the processes according to some embodiments of the presentinvention utilize specifically formulated multi-component inkcompositions having compatible agents which are capable of interactingtherebetween on the surface of the substrate to form an elastic filmwhile not being absorbed into the substrate due to the combination ofspecific chemical formulation and particular printing processparameters, as detailed hereinbelow.

Hence, according to an aspect of the present invention, there isprovided a proto-elastomeric film-forming inkjet composition whichincludes a first part and a second part, wherein the first partcomprises an emulsified property-adjusting agent and a first carrier,and the second part comprises a property-sensitive proto-elastomericfilm-forming agent, a colorant and a second carrier, whereas the secondpart congeals or coagulates upon contact with the property-adjustingagent.

The inkjet composition, according to embodiments of the presentinvention, is formulated for forming an image in a form of an elasticfilm attached to a surface of a stretchable and/or flexible substrate.

Once all the parts of the ink composition converge on the substrate andthe printing process is complete, a thin elastic film, which constitutesthe image, is formed on the substrate. As used herein, the phrase“elastic film” refers to the mechanical property and form of the image,as it is formed on the substrate from a polymerizable ink composition.This film is said to be elastic since it is formed substantially fromelastomeric substances. The film, according to some embodiments of thepresent invention, is at least as elastic as the substrate it is affixedto.

The term “elastomeric”, as used herein, refers to the mechanicalproperties of a rubber-like polymeric substance, which can deform understress exerted by external forces, and can return to its original shapewhen the stress is removed. The elasticity of an elastomer may depend onexternal conditions such as temperature. Hence, according to someembodiments, the term “elastomeric” refers to mechanical properties attemperatures which are normal for human habitats, and particularly atroom temperature.

Hence, the elastomeric film which constitutes the image is characterizedby a low glass transition temperature (Tg), which allows it to form astretchable image on a stretchable substrate at ambient conditions. Theglass transition temperature (Tg) is the temperature below whichamorphous materials, such as polymers, become stiff (glassy), and abovewhich become pliable and elastic (rubbery).

“Thermoplastic” is another term which is used to describe polymericsubstances which can reversibly go from a stiff state to an elasticstate.

As used herein, the term “thermoplastic” refers to a polymer which issufficiently soft above a certain temperature so as to readily allowplastic deformation of the polymer, and which is sufficiently stiffbelow a certain temperature so as to retain a desired shape. Thesoftening of a thermoplastic polymer often occurs at temperatures nearand/or above a transition temperature (e.g., a glass transitiontemperature, a melting point) of the polymer. Such a transitiontemperature may be determined, for example, by calorimetry.

The phrase “softening temperature”, as used herein, refers to the lowesttemperature among the glass transition temperature range of athermoplastic polymer. Other terms used in the art for suchtemperature-dependent characteristic, include the melting point of thethermoplastic resin, the temperature which brings the viscosity of thethermoplastic resin to about 10¹¹ to 10¹² poises, the pour point of thethermoplastic polymer, and the minimum film-forming temperature (MFT) inthe form of an emulsion of the thermoplastic polymer.

In the context of embodiments of the present invention, the relativelylow Tg of the finished image film attached to the substrate is lowerthan 0° C., or alternatively it ranges from about −35° C. to about 0°C., or from about −35° C. to about −5° C.

The property of Tg of the film is determined by the properties of itsconstituents, therefore a film which is elastic at relatively lowtemperatures, is formed from elastomers having a relatively low Tg.Hence, according to some embodiments of the present invention, the inkcomposition which forms can form a film which is affixed to thesubstrate comprises proto-elastomeric film forming constituents.

The elasticity of the elastomeric film which constitutes the image canbe determined by its ability not to crack or tear when the substrate onwhich it is applied on is stretched. For example, an image is defined aselastic in the context of embodiments of the present invention, ifmaintains its shape, color composition and overall integrity (no cracks,tears or other permanent deformations) upon stretching the substrate inone direction by 30% of its original length. Alternatively, an image isdefined as elastic when maintaining integrity after substrate isstretched by 50%, 75%, 100%, 150%, 200% and up to 300% for highlystretchable substrates.

Alternatively, the image is defined as characterized by an elongationpercentage and a recovery percentage of elongation, when it maintainsits original shape and color composition and is fully recoverable afterstretching when applied on a given substrate. The elongation percentageand a recovery percentage of elongation are as defined in U.S. Pat. No.5,874,372. Hence, the elastic image afforded according to someembodiments of the present invention, is characterized by an elongationpercentage of 30% to 200% and a recovery percentage of elongation of atleast 70%.

As used herein, the term “proto-elastomeric” refers to a substance whichbecomes elastomeric, as defined herein, under certain conditions, suchas setting, polymerizing, drying, heating, curing, crosslinking and thelikes. For example, crude natural rubber becomes elastomeric uponvulcanization, which is a chemical process involving heat andcrosslinking with sulfur. In the context of embodiments of the presentinvention, a proto-elastomeric substance may be found in a dispersedform, a dissolved form or as an emulsion, and in the process ofpolymerization, self-crosslinking, crosslinking via a crosslinkingagent, drying and/or curing, becomes the elastomeric substance which isleft attached on the surface of the substrate.

The phrase “film-forming agent”, as used herein, refers to abonding/binding agent (binder) which polymerizes, crosslinks to itselfor crosslinks via a crosslinking agent, and affords a film or a layerupon application, optionally upon drying and curing thereof on asurface. As known in the art, film-forming agents are a group ofchemicals that afford a pliable, stretchable, cohesive, and continuousor semi-continuous covering film or layer over a surface when appliedthereon and allowed to undergo a chemical or physical transition. Thechemical or physical transition may be setting, polymerizing, drying,heating, curing, crosslinking and the likes. The phrase “film-formingagent”, encompasses coating agents, binders, adhesives,adhesion-promoting agents, resins, polymers, co-polymers and the likecollectively.

Non-limiting families of film-forming agents include monomers, oligomers(short chains of about 10-100 monomers), polymers and copolymers ofacrylates, acrylamides and other derivatives of acrylic acid,acryl/styrene, polyethylene-glycols, urethanes andpolyvinylpyrrolidones, and the likes also in the form of resin emulsionsand co-emulsions. These film-forming agents can also be selected to havea relatively low Tg.

In order to obtain a sharp and vivid image in the form of an elasticfilm, the film should be made from fine and distinct points of colors,corresponding to pixels of a digital image or the grain of aphotographic paper coated with light-sensitive chemicals. The distinctpoints of colors stem from very fine droplets of colored ink which arejetted onto the substrate during the printing process, and the finer thedroplets remain on the substrate after ejection, the finer the imagewould be. The droplets will remain fine if feathering, bleeding andsmearing can be limited.

As discussed hereinabove, the way to afford a sharp image film on thesubstrate is to “freeze” or immobilize the droplets on contact with thesubstrate. Thus, a chemical and/or physical change takes effect in theink composition upon contacting thereof with the substrate, and thischemical and/or physical change is effected by combining agents in thecomposition which are designed to afford the immobilization of theinkjet droplets on the substrate, which will eventually lead to betterand sharper images.

The term “immobilization”, as used in the context of embodiments of thepresent invention, refers to the act of restriction or substantiallimitation of flowability of a liquid, namely substantial reduction ofthe capability of a liquid to move by flow. For example, immobilizationof a liquid can be effected by congelation of the liquid or solutestherein. Immobilization of droplets of liquid ink can be achieved, forexample, by elevating the viscosity of the liquid ink composition suchthat the droplets are restricted from flowing once in contact with thesubstrate. As used herein, the term “immobilization” is not meant toinclude final polymerization and print fixation by crosslinking andcuring reactions.

Quantitatively, “immobilization” in the context of embodiment of thepresent invention is defined as elevating the viscosity of thecolor-bearing parts of the ink composition by 10-folds, 50-folds,100-folds, 500-folds 1000-folds or 2000-folds and more. For example,when a given color-bearing part is characterized by having a viscosityof 10-13 cp, it is defined as immobilized when its viscosity is elevatedto about 2000 cp or higher as a result of congelation.

Hence the chemical and/or physical change, according to some embodimentsof the present invention, is congelation. The term “congelation”, asused herein, is synonymous to the terms “coagulation”, “thickening” or“gelation”, and refer to the sharp decrease in fluidity of a formerlyfluid liquid. Congelation can be effected also by sedimentation,precipitation, partial solidification and partial polymerization ofsoluble constituents in the composition.

Thus, according to some embodiments of the present invention, the inkjetcompositions include an emulsified proto-elastomeric film-forming agentthat can congeal on a stretchable substrate controllably so as to avoidbleeding of the ink composition. The ink composition then polymerizesduring drying/curing on the surface of the substrate without beingabsorbed therein, and becomes affixed to the substrate, therebyaffording an image in the form of a flexible film, which can staypliable and extendable as the stretchable substrate at normaltemperatures of everyday life.

A flexible film-shaped image in the context of the present is defined byhaving a Young's modulus of less than 2 GPa, less than 1 GPa or lessthan 0.5 GPa.

In order to effect congelation upon contact with the substrate and notbefore, the proto-elastomeric film-forming ink composition is formedfrom at least two separate parts which combine only upon contact withthe substrate. The two parts cross-react with each other since one partcontains a property-sensitive proto-elastomeric film-forming agent andthe other contains a property-adjusting agent, and the cross-reactionbetween the two parts effects the congelation.

In general, the objective of using a multi-part ink compositioncontaining property-sensitive proto-elastomeric film-forming agent inone part and property-adjusting agent in a separate part, is to providethe means to congeal and thereby immobilize the ink composition only onthe surface of the substrate and not beforehand, thus avoiding cloggingof the delicate elements of the printheads. The property-adjusting agentis selected such that it effects a change in the property-sensitivefilm-forming agent only upon allowing contact therebetween, and therebyeffects congelation in the combined ink composition.

The term “property-sensitive” refers to a component of a compositionwhich is sensitive to a change in a particular chemical and/or physicalproperty of the composition and as a result of such a change undergoes achemical and/or physical change which effects the entire composition.Such sensitivity can manifest itself by, for example, the loss of itsability to stay as an emulsion, an event that leads to congelation.

The term “property” as used herein refers to a chemical and/or physicalproperty of the ink composition, namely, a characteristic of thecomposition that is reflected by the chemical composition and/or aphysical parameter of the composition. Representative examples include,without limitation, acidity (pH), metal atom complexation,dispensability, dispersibility, solubility, ionic strength,hydrophobicity, electric charge and the likes.

The term “pH” refers to the quantitative measure of the acidity oralkalinity (basicity) of liquid solutions. As will be discussedhereinbelow, the present inventors have found that someproto-elastomeric film-forming agents become pH-sensitive only in thepresence of certain metal oxides.

The phrase “metal ion complexation”, as used herein, refers to theability of some functional groups in certain substances, to act asligands which bind to some metal atoms in a coordinative manner so as toform a metal-ligand complex. Such complexation may alter the chemicalcharacteristics of these substances and render them more or lesssusceptible to chemical changes in their environment. As will bediscussed hereinbelow, the present inventors have found that someproto-elastomeric film-forming agents are sensitive to this propertywithout the need of a change in the pH of the medium.

The phrase “ionic strength” as used herein refers to the charge-weightedconcentration of ions in solutions.

The term “hydrophobicity” as used herein refers to a quality of anon-polar molecule or group that has little affinity to water or otherpolar solvents. Hydrophobic groups on molecules in a polar solution tendto turn in on them or clump together with other hydrophobic groups.

The term “dispersibility” as used herein refers to the amount of adispersed or emulsified species that will disperse in a specific carrierunder given conditions. The reduction of dispersibility may be effectedby a change in another chemical property such as pH, ionic strength,hydrophobicity or otherwise causing collapse of the dispersion oremulsion.

The aforementioned properties may be inter-dependent, namely a change inone property effects a change in another property, thereby constitutinginter-dependency therebetween. An example of such inter-dependency is apH-dependent dispersibility and ionic-strength-dependent dispersibility,wherein the change in pH (the aforementioned acidity or alkalinityproperty) or the ionic-strength of a solution changes the dispersibilityof one or more of its dispersed species.

Similarly, there exist inter-dependency between metal ion complexationcombined with pH, and the capacity to stay emulsified (dispersed), andsuch interdependency is discussed in detailed hereinbelow.

The phrase “property-adjusting agent” as used herein refers to acomponent in a part of a multi-part ink composition and can effect thelevel of one or more chemical or physical properties of other parts ofthe composition when these compatible parts come in contact and combine,such as a pH level, metal-ion-ligand complexation, dispersibility, theionic strength, the hydrophobicity or the electric charge/valency of thecombined composition. By effecting a change in one or more suchproperties, the property-adjusting agent is causing theproperty-sensitive proto-elastomeric film-forming agent to undergo achemical and/or physical change (such as congelation), as discussedherein.

According to some embodiments of the present invention, the first partof the multi-parts ink composition is formulated with a first carrier(solvent) and used to carry and deliver a property-adjusting agent, anddoes not contain a colorant and is thus substantially transparent andcolorless, and intended not to leave a distinguishable mark on thesubstrate. It is the property-adjusting agent that affects aproperty-sensitive proto-elastomeric film-forming agent in a secondcolor-bearing part and other optional parts of the ink composition,thereby effecting congelation of the combined parts. Hence, the firstpart of the ink composition, which includes a property-adjusting agent,is also referred to herein interchangeably as the immobilization part.The second part of the ink composition, comprises a colorant, a secondcarrier and a property-sensitive proto-elastomeric film-forming agent inthe form of, for example, an emulsified resin, which will congeal on thesurface of the substrate due to an interaction between the parts (e.g.,an interaction induced by the property-adjusting agent). According tosome embodiments of the invention, an ingredient of the ink compositionwhich imparts elastic stretchability, is the property-sensitiveproto-elastomeric film-forming agent. Optionally or additionally, theelastic stretchability is imparted by an additional binder which is notnecessarily property-sensitive. As discussed hereinabove, when theseconstituents co-polymerize, crosslink and cure and thereby affix to thesubstrate, a soft, flexible and stretchable elastic film is formed whichis characterized by a relatively low Tg.

The present inventors have found that emulsions of someproto-elastomeric film-forming agent will be stable in variousconditions, such as low pH, but will break and congeal if a certainmetal oxide is present in the emulsion. Hence according to someembodiments of the present invention, the second part of the inkcomposition further includes a first metal oxide, as this phrase isdefined hereinbelow.

According to some embodiments of the present invention, theproto-elastomeric film-forming agent can be a polymerizable agent, whichis soluble/dispersible/emulsifiable when present in the ink compositionand may also act as a proto-elastomeric film-forming dispersing agentfor the various pigment colorants which are included in some parts ofthe ink composition. This proto-elastomeric film-forming colorantdispersing agent, can be the property-sensitive agent that congealswhen, for example, a transition metal oxide is added and/or the pH orthe ionic strength of the media it is dissolved in crosses a certainlevel. Hence, according to some embodiments of the present invention,the proto-elastomeric film-forming attribute, and the property-sensitiveattribute are combined in a dispersant of colorants. However, accordingto other embodiments of the present invention the proto-elastomericfilm-forming agent is not required to disperse the colorant(s) or beassociated therewith in any form.

The term “colorant” as used herein describes a substance which impartsthe desired color to the printed image. The colorant may be a pigment ora dye. Pigments are solid colorants with are typically suspended in thecarrier of the ink composition as dispersed particles, whereby dyes arecolorants which are dissolved in the carrier of the ink composition.Some dyes may be insoluble liquids which form emulsions with thecarrier.

A typical colorant in inkjet ink compositions is a dispersed pigment. Asfound by the present inventors, the property-sensitive proto-elastomericfilm forming agent according to embodiments of the present invention, isnot necessarily involved with the colorant, may it be a dispersedpigment, a dissolved dye or combinations thereof. Therefore thisproperty-sensitive proto-elastomeric film forming agent can serve itspurpose in the context of embodiments of the present invention withoutreference to the colorant, as opposed to some ink compositions known inthe art, where the colorant in a dispersed pigment and the pigment'sdispersant is sensitive to pH or other effectors. For example, accordingto some embodiments of the present invention, such dispersant areacrylic salts (salts of an acrylic acid monomer), which lose theirdispersing attribute and become immiscible or insoluble as a result of apH-shift.

For example, a property-sensitive proto-elastomeric film-forming agent,such as a pH/metal-ion-sensitive acrylic polymer or copolymer, can loseits ability to stay in an emulsified form, possibly due to formation ofmetal-complexation species when the pH of the liquid formulation dropsbelow a certain level and/or when a certain metal ion or metal oxide isintroduced, thus effecting congelation of the combined ink compositionand in practice effects the immobilization of the colorant which ispresent therein.

Hence, according to some embodiments, the property-sensitiveproto-elastomeric film-forming agent does not serve as a dispersant forthe pigments, but rather affects the dispersability of the pigments inan indirect fashion by congealing and thus immobilizing the pigments aswell.

The basic process colorants in liquid ink compositions are required tobe transparent or translucent, since only a few (typically 3-8) basiccolors are used and the full spectrum of colors and shades is achievedwhen these basic colors are perceived by the eye as mixed in variouscombinations on the substrate. However, direct printing of multicolorimages using transparent inks on any surface requires the surface, whichis the background of the image, to be white or at least lightly-colored,since its inherent color participates in the formation of the finalperceived color, together with the colorant in the inks applied thereon.Surfaces of darkly colored or non-white substrates tend to render theprimary-colored ink drops indistinguishable or substantiallycolor-skewed since the final perceived color stemming from anycombination of the primary colors is a subtraction of that particularcombination from the color white, or at least from a bright light color.It is therefore a physical requirement that the background of an imagegenerated directly onto a surface be a bright light color or white.

To overcome the problem of printing on a non-white substrate, an opaquewhite underbase layer is printed on the substrate before the translucentcolored part (second part) is printed. This opaque underbase layer isafforded by a third part of the ink composition, according to someembodiments of the present invention.

Hence, according to some embodiments of the present invention, the inkcomposition further includes a third part which comprises an emulsifiedproperty-sensitive proto-elastomeric film-forming agent, an opaquecolorant in the form of a second metal oxide, as this phrase is definedhereinbelow, and a third carrier.

The third part therefore includes an opaque and lightly-colored pigmentcolorant. According to some embodiments, the opaque and lightly-coloredopaque pigment colorant is white, affording an opaque white layer whenjetted on a darkly-colored or non-white surface. According to someembodiments, the white opaque pigment is suitable-sized particles of asecond metal oxide, such as, for example, titania. In order to serve asan underbase for a stretchable and flexible image, the opaque underbaseshould also be stretchable, with a high elongation factor that enablesthe image printed thereon to maintain its background when stretched withthe substrate, without having the (colored) substrate to be seentherethrough and without having the image or the underbase crack underphysical pull and tug.

The ink composition, according to some embodiments of the presentinvention, is suitable for inkjet printing of “spot” colorants, whichare substantially opaque colored inks. Spot colorant can be jetted likeany other transparent “process” colorants, and are typically used togenerate special effects in order to afford highlights and emphases overthe image usually in pre-defined coloration.

Hence, according to some embodiments of the present invention, themulti-part ink composition further includes a fourth part whichcomprises an emulsified property-sensitive proto-elastomericfilm-forming agent, a second metal oxide which is substantially opaque,a colorant and a fourth carrier. The table below presents the variousparts of the ink composition, according to some embodiments of thepresent invention, and lists their alternative names used herein, theirfunction and some of their principle ingredients. It is noted that thewetting composition, which is discussed in details hereinbelow in thecontext of a process for printing the image, may be regarded as anotherpart of the composition albeit it is not necessarily applied on thesubstrate by digital means or an inkjet printhead.

Multi-part ink composition Term in Alternative term claims andcharacteristics Function Principal ingredients Wetting Typically appliedby To flatten protruding Water composition massive spraying and canfibers, smooth and further be manipulated even the surface mechanicallyby before fine droplets squeegee or roller are printed thereon Firstpart Immobilization part; Provides the property- A property-adjustingagent Generally adjusting agent, (e.g. an acid); transparent/colorless;namely the constituent A carrier (e.g. water); Typically printed beforethat causes the ink An optional polymerizable or concurrently with thepart that contains the resin (e.g. an acrylic mixture) other parts andafter the property-sensitive wetting composition agent to congeal oncontact Optionally provides some of the proto- elastomeric film formingagent(s) Second part Colored part; Provides the colorants A dispersedtranslucent Translucent color part; for the design/image colorant;Generally transparent which are dispersed in A carrier (e.g. water); andcolored by CMYK a property-sensitive A property-sensitive basic colors;dispersant that polymerizable dispersant Typically printed aftercongeals upon contact (e.g. an acrylate); and over the first part withthe first part; An optional additional Provides some of thepolymerizable resin (e.g. proto-elastomeric film an acrylic mixture);forming agent(s) A polymerization catalyst; A crosslinking agent; Thirdpart Underbase part; Provides a solid A dispersed opaque colorant Opaquewhite part; opaque white (e.g. a metal oxide); Generally opaque andbackground to the A carrier (e.g. water); white; translucent colors Aproperty-sensitive Typically printed after when printed on apolymerizable dispersant and over the first part non-white substrate;(e.g. an acrylate); and before the second Provides some of the Anoptional additional part. proto-elastomeric film polymerizable resin(e.g. forming agent(s) an acrylic mixture); A polymerization catalyst; Acrosslinking agent; Fourth part Spot color part; Provides a “non- Adispersed opaque colorant Opaque colored part; process” solid opaque(e.g. a metal oxide); Typically printed after colored highlights of Adispersed translucent and over the second part color over the colorant;design/image; A carrier (e.g. water); Provides some of the Aproperty-sensitive proto-elastomeric film polymerizable dispersantforming agent(s) (e.g.a n acrylate); An optional additionalpolymerizable resin (e.g. an acrylic mixture); A polymerizationcatalyst; A crosslinking agent;

The action of immobilization by congelation of the ink composition iseffected upon the abovementioned chemical or physical property changecaused by the property-adjusting agent that is delivered concomitantlywith the property-sensitive proto-elastomeric film-forming agent. Thisinstant immobilization by congelation of the jetted dropletssubsequently promotes improved color and detail resolution of the image,as well as improved contact between the colorant(s) in the inkcomposition and the substrate, which is effected by better adhesion ofthe medium containing the colorant (pigment and/or dye) therein to thesubstrate. The binding and adhesion of the medium containing thecolorant may be effected by, for example, direct heat-activated chemicalcrosslinking or entanglement of the proto-elastomeric polymerizablecomponents in the ink composition with functional groups in thesubstrate.

In general, the content of the various parts of the ink composition,according to embodiments of the present invention, may vary according tothe type of substrate and the specific requirements of the final printedproduct, yet each serve the same principles as follows. The carrier isselected to provide a medium for mixing, suspending and/or dissolvingthe other components of the ink composition, and is required to bevolatile and benign. The colorant is selected to achieve the desirablecolor and other physical and chemical properties, and be suitable for agiven printing machine, printheads and printing technology. The variousproto-elastomeric film-forming binders and adhesion promoting agents aswell as their activating and catalyzing counterparts, when needed, areselected so as to afford the adhesion of the colorants to the surface ofthe substrate in a substantially irreversible manner, at least in thesense of normal use of the final product as well as capable of formingan elastic film, and therefore should provide sustainability,stretchability and flexibility of the image on the product in wash, dryand reasonable wear and tear.

The inkjet ink composition according to some embodiments of the presentinvention, are formulated so as to be suitable for use in an inkjetprinting process. Hence, the ink compositions presented herein areformulated so as to exhibit general attributes for each of its parts,other than color and chemical composition. Thus, in some embodiments,the ink composition is further characterized by attributes such asdynamic viscosity (standardized 35° C.), surface tension, sonicvelocity, pH, maximal dispersed particle size, carrier volatility,chemical stability, bacteriostatic and anti-corrosive attributes, aswell as other characteristics which are more particular to certaininkjet techniques such as electric resistance/conductance,polarizability, irradiation sensitivity and electrostatic, piezoelectricand magnetic attributes, as these terms are known to any artisan skilledin the art.

Each of the parts of the ink compositions used in the process presentedherein therefore exhibits, among other properties, the followingphysicochemical properties which render it suitable for inkjet printing,namely:

Dynamic viscosity that ranges from about 1 centipoise (cP) to about 150cP, or from about 8 cP to about 25 cP, or from about 8 cP to about 20cP, or from about 8 cP to about 15 cP at typical working (jetting)temperature that ranges from about 30° C. to about 45° C.;

Surface tension that ranges from about 25 N/m to about 41 N/m;

Maximal particle size lower than about 1 micron (μm);

Electrical resistance that ranges from about 50 ohms per centimeter toabout 2000 ohms per centimeter; and

Sonic velocity that ranges from about 1200 meters per second to about1800 meters per second.

As a typical printhead is resistant to pH of 4-10, the final pH of anypart of the ink composition should be within these limits.

According to some embodiments, each part of the ink composition exhibitsa dynamic viscosity at room temperature of about 11 centipoises, asurface tension of about 31 dynes per centimeter and a maximal particlesize lower than 1 micron.

The ink compositions, according to some embodiments of the presentinvention, are formulated so as to polymerize and adhere to thesubstrate, preferably upon curing by heat.

Following are descriptions and examples of various ingredients of thevarious part of the ink composition.

Exemplary property-sensitive proto-elastomeric film forming agentsinclude, without limitation, non-ionic water-emulsifiable resins such asacrylic polymers and copolymers, alkyl-acrylic polymers and copolymers,acrylic-styrene copolymers, polyurethanes, polyethers, polyesters,polyacrylates and some combinations thereof.

According to some embodiments of the present invention, theproperty-sensitive proto-elastomeric film-forming agent is aself-crosslinking alkyl-acrylic copolymer, and according to someembodiments, the self-crosslinking alkyl-acrylic copolymer is anethyl-acrylic/butyl-acrylic copolymer.

Some acrylic-based polymers and copolymers are emulsifiableself-crosslinking polymers which are used in the garment industry tobestow physical and chemical resistance to the cloth, knitted, woven ornon-woven, against physical wear and tear due to frequent use andrepeated washing, as well as against alcohol, organic solvents andwater.

When selected to have a low Tg, according to embodiments of the presentinvention, suitable property-sensitive proto-elastomeric film formingagents which are commercially available, include without limitation,TEXICRYL™ 13-216 (Tg −14° C.), TEXICRYL™ 13-290 (Tg −30° C.), TEXICRYL™13-297 (Tg −9° C.) and TEXICRYL™ 13-326 (Tg −25° C.) which arecommercially available from Scott Bader Ltd., and APPRETAN™ E 2100 (Tg−30° C.), APPRETAN™ E 6200 (Tg −20° C. and APPRETAN™ E 4250 (Tg −15° C.)which are commercially available from Clariant.

Other non-limiting examples of commercially available property-sensitiveproto-elastomeric film-forming agent which do not serve as pigmentdispersants include ACRYSOL™ series, commercially available from Rhomeand Hass Ltd., and ACRONAL™ series, commercially available from BASFInc.

Other binders, dispersants and adhesion promoters which are useful inthe context of a proto-elastomeric film-forming agent according toembodiments of the present invention include, without limitation,commercially available and widely used families of products, known undernames such as Alkydal™, Desmodur™ and Desmophen™ (from Bayer);Beckopox™, Macrynal™, Maprenal™, Viacryl™ and Vialkyd™ (from VianovaResins); Cythane™ (from Cytec); Dynapol™ and Vestanat™ (from Hiils);Johncryl™ (from Johnson); K-Flex™ (from King Industries); Synocure™ andSynolac™ (from Cray Valley); Synthalat™ (from Synthopol); Tolonate™(from Rhone Poulenc); Uracron™ and Uralac™ (from DSM); Worleecryl™ andWorleekyd™ (from Worlee) and the likes.

It is noted that any exemplary ingredient disclosed herein is given forexemplifying purposes only, and should not be regarded as limiting tothat particular ingredient or commercially available product, but ratherregarded as a representative member of a wider group of alternatives,all of which are meant to be encompassed in the context of otherembodiments of the present invention.

Another purpose of using film-forming agents is overcoming loose andprotruding fibers during the printing process on knitted, woven andnon-woven fabrics. Flattening these fibers, even only for the durationof the printing process, ultimately affords a sharper image altogether.This additional effect is readily afforded since most of the suitableproto-elastomeric film-forming agents according to some embodiments ofthe present invention, are sticky binders.

Typically, the concentration of the property-sensitive proto-elastomericfilm-forming agent can range from about 10 weight percentage to about 50weight percentages of the total weight of the relevant part of themulti-part ink composition.

The abovementioned property-sensitive agents can be readily affected byadding a chemical substance (the property-adjusting agent) which lowersor elevates the level of the properties listed under the term “property”hereinabove. For example, adding an acid (H+ ions) will elevate theacidity while adding a base will lower the acidity level, and thusaffect a pH-sensitive agent such as acrylic resin thickeners (e.g.,carbomers and other rheology modifiers such as members of the CARBOPOLseries, or PEG-based thickeners (e.g., members of the ACRYSOL RM™series) and the likes.

Similarly adding a salt (ions of a particular valency) will elevate theionic strength, adding a precipitating agent will lower the solubility,adding a hydrophilic agent will lower the hydrophobicity, adding acharged species will elevate the electric charge, and so on, eachproperty can be lowered or elevated by use of a suitable adjustingagent.

Exemplary property-adjusting agents which may be use in context ofembodiments of the present invention, include acids and/or bases thatadjust the pH property; metal oxides, salts that adjust the ionicstrength and electrical charge; or oxidizing agents, reducing agents,radical-producing agents and crosslinking agents which change thechemical reactivity of certain chemical groups present in one or morecomponents of the other part of the ink composition and thereby effectthe solubility thereof by promoting crosslinking and/or polymerizationof these components. The crosslinking agent may also promote theadhesion of the colorant to the substrate by chemically interacting withfunctional groups on the surface, as these terms are definedhereinbelow.

The following describes a few representative and non-limiting examples,which present how the objective of using the property-sensitiveproto-elastomeric film-forming agent and property-adjusting agent ismet:

An acid-base interaction can cause a dispersing agent or aproto-elastomeric film-forming agent that is soluble in a basic orneutral composition to precipitate once it comes in contact with anacid. Similarly, an emulsified film-forming agent may no longer hold anemulsion as a result of a decrease in pH. In any such occurrence, thecomposition experiences a sharp increase in the viscosity, orcongelation.

The presence of a metal oxide, such as titanium dioxide or silicondioxide, affects a family of non-ionic acrylic polymers so as to becomesensitive to a drop in the pH of the medium they are emulsified in.Hence, according to some embodiments of the present invention, suchclass of metal oxides is referred to herein as a first and a secondmetal oxide. Such metal oxides do not cause the breakage of the emulsionby themselves, but rather bestow pH-sensitivity to the emulsifiedspecies. It is a matter of mechanistic theory to regard such metaloxides as direct property-adjusting agents, however in the context ofembodiments of the present invention this assignment can be made oravoided without being bound to any particular theory.

Thus, the phrase “first metal oxide” and/or “second metal oxide”, asused herein, refer to metal oxides that is capable of affecting aproto-elastomeric film forming agent so as to become property-sensitive.Such metal oxides include titanium dioxide (also referred to herein astitania, TiO₂) and silicon dioxide (also referred to herein as silica,fumed silica, SiO₂).

Metal oxides are solids that can be grinded into particular particlesize. In the case of titania, the particle size will determine itsability to reflect light, where larger particles will reflect light andthus appear as opaque white, and very small particles thereof, namely inthe order of magnitude of nanometer scale, will be substantiallytransparent to light. Other metal oxide particles can be made positivelycharged, and in the case of fumed silica, positively charged silicaparticles also appear substantially transparent to light. These lightreflecting qualities differentiate the first and second metal oxideclasses into substantially transparent for the first metal oxide class,and substantially opaque white for the second metal oxide class.

A third metal oxide class is regarded as a direct and independentproperty-adjusting agent, since it effects the chemical/physical changein the property-sensitive agent without the presence of anothereffector, such as an acid. Thus, the phrase “third metal oxide” refersherein to a class of metal oxides that can directly effect congelationof the ink composition.

Addition of a small amount of an amphiphilic solvent, such as acetone orwater miscible ketone, may cause emulsion collapse and/or congelationand/or otherwise taking the colorant out of the dispersed state.

A property-sensitive agent being soluble in an aqueous solution willprecipitate once it comes in contact with calcium and/or aluminum ionsand other di- and tri-valent cations, whereupon it will precipitate andwill effect a sharp increase in the viscosity of the combined parts ofthe composition.

A salt (ionic) interaction between anions and cations can cause asuspension or an emulsion to break, namely effect precipitate of itsparticulate components. Preferred salts for effecting an increase on theionic strength include calcium salts such as calcium chloride andcalcium acetate, and aluminum salts such as aluminum chloride andaluminum sulfate, and any combination thereof.

Quaternary cationic surfactants are suitable candidates for effectingcongelation of the emulsified or dispersed polymers and pigments.Non-limiting examples for quaternary cationic surfactants includeflocking products such as PAM (polyacrylamine), SUPERTFLOC™ C440 series(by Cytec), and benzalkonium salts such as benzalkonium chloride.

A hydrophilic-hydrophobic interaction between various solvents such asacetone alcohol, acetone, isopropyl alcohol, ethyl alcohol, andpolymeric latex resin that causes the resin to swell and precipitate andeffect an overall rise in the viscosity of the combined composition.

For example, adding polyvinyl alcohol with a low molecular weight to onepart of the ink composition and adding borax (sodium tetra borate) tothe other part of the composition will cause the formation of a gel uponcontacting these two parts. A similar effect will be achieved when usingcalcium acetate and isopropanol or ethanol, however higher alcohols donot afford the same result.

According to some embodiments of the present invention, the chemicalproperty is pH, and the corresponding property-adjusting agent is abase. An exemplary basic property-adjusting agent is an amine, such as,without limitation, DEA, ammonia, TEA and alike, that may react with acorresponding property-sensitive proto-elastomeric film-forming agent,such as a thickener or a dispersing agent.

According to other embodiments of the present invention, the chemicalproperty is pH, and the corresponding property-adjusting agent is anacid. Although most acids will cause a pH-sensitive proto-elastomericfilm-forming agent to congeal, only some acids will be suitable for theink composition presented herein, which is formulated for inkjetprinting, particularly on textile application.

One exemplary acidic property-adjusting agent is an organic acid.According to some embodiments, the organic acid is a carboxylic acid.Suitable organic acids include, but are not limited to a carbonic acid,a formic acid, an acetic acid, a propionic acid, a butanoic acid, anα-hydroxy acid such as glycolic acid and lactic acid, a halogenatedderivative thereof and any combination thereof.

The selection of a suitable property-adjusting agent in the form of anacid should take into account several factors, namely the corrosivenature of acids on the fabric as well as on the delicate parts of theprinting apparatus and particularly the printheads and other metallicand otherwise delicate parts of the printing machine which corrodeeasily, as well as the tendency of acids to scorch and degrade certainsubstrate materials over time. Hence, the acid should be effectiveenough to cause the desired property-adjusting effect, mild enough so asnot to generate damage to the machinery and/or garment, and transitoryso as not to degrade the finished product.

According to some embodiments of the present invention, acids which maybe neutralized by heat are jointly referred to herein as transitoryacids. Hence, the phrase “transitory acid”, as used herein, refers to anacid which can be rid of by the virtue of being volatile orintra/cross-reactive to form essentially neutral species.

While evaporation is one mechanism by which heat can reduce the presenceof a volatile acid, heat can also reduce acidity in other ways. Someacid compounds may exhibit pH variability over a range of physicalconditions, such as temperature. For example, some organic acidcompounds may undergo a chemical reaction, such as condensations, uponapplying heat to the composition. This chemical reaction ultimatelyleads to loss of the acidic property and an elevation and neutralizationof the pH in the finished product after curing, which typically involvesheating.

It is noted herein that in general alpha-hydroxy acids are suitable as atransitory acid according to some embodiments of the present invention.

For example, lactic acid may be used to bring the pH of an aqueoussolution to about 2-3 (pKa of 3.8 at 25° C. in water), but when heatedabove 100° C. in dehydrating conditions, lactic acid molecules reactwith one-another to afford the neutral and stable lactone specie know aslactide, which is the cyclic di-ester of lactic acid. Lactide mayundergo further transformation and participate in the polymerizationreaction on the substrate, as lactide is known to lead to the formationof PLA, poly-lactic acid polymers and co-polymers.

Another example for such a transitory acid is glycolic acid, which formsthe cyclic and neutral lactone 1,4-dioxane-2,5-dione.

Transitoriness is required when it is desirable to have little or notraces of an acid in the final product. Therefore acid traces should bereduced before or during the curing step of the process (effectedtypically at 140-160° C.), and can no longer damage the substrate. Onthe other hand, the fumes of too-volatile acid will seep into theorifices, at print off-time, reacting with the other parts of the inkcomposition, causing immediate printhead blockage, and in longer timeterms will cause corrosion of sensitive elements of the printing machineand the environment. Another factor is the workers health which may beadversely effected by highly volatile acid such as formic acid. Inaddition, some volatile acids cause noxious or unpleasant odor even ifminute reminiscence thereof is left in the finished product. Somevolatile acids leave a distinct and mostly unpleasant odor, andtherefore should be disfavored as noxious odor may affect the work placeas well as cause malodor of the product at the end-user side. Hence, anodorless volatile or otherwise transitory organic acid should beselected when possible.

Exemplary transitory organic acids which can provide all the aboveadvantages with minimal disadvantages include, but are not limited to,lactic acid and glycolic acid.

Hence according to some embodiments, the acid is glycolic acid or lacticacid. The acid may be buffered by a weak amine such astris(hydroxymethyl aminomethane), also referred to as Tris or THAM.

According to some embodiments, an acidic immobilization part may bebuffered by a suitable salt or weak base, such as ammonia/ammonium baseor another volatile amine, to ensure full extraction of any traces ofacid or base in the printed image.

According to some embodiments of the present invention, the chemicalproperty is metal-ion complexation, and an exemplary correspondingchemical property-adjusting proto-elastomeric film-forming agent is anemulsified non-ionic polymer. An exemplary metal-atom complexationproperty-adjusting agent is nano-sized particles of titania(nano-titania), fumed silica or alumina, as discussed hereinabove incontext of the third metal oxide.

Other property-adjusting agents suitable for this application are waterimmiscible solvents such as alcohols. While using these inflammableliquids great care must be taken to avoid fire hazards, especiallyduring the initial drying period when high concentration of alcoholfumes are present in the vicinity of a heat source.

Hence, low alcohols, such as ethanol and isopropyl alcohol, react fastenough in the ink (so as to affect the emulsion and/or dispersion) toobtain acceptable immobilization. These reagents affect the emulsionstability, thus causing the above-described opaque and colored parts tocongeal on the substrate's surface.

The concentration of the property-adjusting agent should correspondadequately to the type and amount of the property-sensitiveproto-elastomeric film-forming agent, and can range from about 0.5% toabout 20% of the total weight of the composition.

According to some embodiments of the present invention, the colorant canbe a liquid dye dissolved or otherwise mixed in the carrier of the inkcomposition, or solid pigment particles dispersed in the inkcomposition. According to some embodiments, the colorant content in theink composition used in the process present herein ranges from about 0.2weight percentage to about 40 weight percentage of the total weight ofthe ink composition. According to other embodiments, the colorantcontent ranges from 1 to 10 weight percentages of the total weight ofthe ink composition. One of the main components of the ink compositionis the carrier.

According to some embodiments, the carrier in each of the parts of theink composition, namely the first carrier, the second carried, the thirdcarrier and the fourth, is an aqueous carrier (e.g., water). However,non-aqueous carriers are also contemplated. The carriers of the variousparts of the ink composition may be identical or different, depending ontheir function and solutes used in each formulation. According to someembodiments of the present invention, the carrier of all the parts ofthe ink composition is an aqueous carrier, namely consisting essentiallyof water, tap water or deionized water. According to some embodimentsthe aqueous carrier may further include one or more organic, includingsolvents acting as humectants, such as propylene glycol, diethyleneglycol and such glycols and/or glycerin.

The ink compositions can be designed such that the polymerizationreaction between the film-forming agents and the substrate would beeffected in the presence of a catalyst, also referred to as apolymerization initiator.

The term “catalyst” as used herein describes a chemical substance whichis capable of promoting, initiating and/or catalyzing the chemicalpolymerization reaction between polimerizable ingredients of the inkcomposition, and to some extent also with the functional groups in thesubstrate directly or via a crosslinking agent. The catalyst, orpolymerization catalyst/initiator, is selected so as to promote,initiate and/or catalyze the reaction upon contact of the inkcomposition with the substrate, optionally in combination with anexternal heat or other forms of radiation that is applied during thecuring of the image.

Hence, according to some embodiments of the present invention thecatalyst is a blocked (salt) acid catalyst or an unblocked (free) acidcatalyst. Exemplary blocked acid catalyst include, without limitation,blocked dinonylnaphthalene sulfonic acid, blocked dinonylnaphthalenedisulfonic acid, blocked dodecylbenzene sulfonic acid, blocked toluenesulfonic acid, a blocked alkyl phosphate acid and a blocked arylphosphate acid.

Exemplary commercially available catalysts include without limitationsblocked acids such as, for example, members of the NACURE™ series,commercially available from King Industries, Inc, Norwalk, Conn., USA,or CYCAT™ series available from Cytec Industries Inc.

An ingredient which can promote the formation of a continuous andstretchable polymeric/co-polymeric film, as well as promote binding andaffixation of the film to the substrate, is a crosslinking agent.

As used herein, the phrase “crosslinking agent” refers to a substancethat promotes or regulates intermolecular covalent, ionic, hydrophobicor other form of bonding between polymer chains, linking them togetherto create a network of chains which result in a more elastic and/orrigid structure. Crosslinking agents, according to some embodiments ofthe present invention, contain at least two reactive groups that caninteract with respective groups present in the polymerizableconstituents of the ink composition and/or the substrate. Exemplary suchreactive groups include, but are not limited to, amine groups, carboxylgroups, hydroxyl groups, double bonds, and sulfhydryl groups.Crosslinking agents include homo-bifunctional crosslinking agents thathave two identical reactive end groups, and hetero-bifunctionalcrosslinking agents which have two different reactive end groups. Thesetwo classes of crosslinking agents differ primarily in the chemicalreaction which is used to effect the crosslinking step, whereinhomo-bifunctional crosslinking agents will require a one step reaction,and hetero-bifunctional crosslinking agents may require two steps toeffect the same. While homo-bifunctional crosslinking agents have thetendency to result in self-conjugation, polymerization, andintracellular crosslinking, hetero-bifunctional agents allow morecontrolled two step reactions, which minimizes undesirableintramolecular cross reaction and polymerization. Crosslinking agentsare further characterized by different spacer arm lengths. Acrosslinking agent with a longer spacer arm may be used where two targetgroups are further apart and when more flexibility is desired.

The type of bonding between the film and the substrate dependssubstantially on the type of substrate, or more specifically, on thephysical micro-structure of the surface, and the availability ofreactive functional groups on the surface of the substrate, namely itschemical composition. Cellulosic materials, such as many fabrics made atleast a partially from natural fibers (cotton, hemp), wool, silk andeven skin and leather, offer a variety of available and reactivefunctional groups such as hydroxyl, carboxyl, thiol and amine groups,which can be tethered to the film via the crosslinking agent.Alternatively, in cases on some substrates such as synthetic polymericsubstrates, the scarcity of reactive functional groups means that thebonding of the film to the substrate is afforded by mechanicalproperties and micro-structure of the surface, namely affixation bypolymeric adhesion and physical interweaving and entanglement.

The crosslinking agent also has an effect on the elasticity of theresulting film. The resulting modification of mechanical properties ofthe polymeric film formed on the substrate depends on the crosslinkdensity, i.e., low crosslink densities raise the viscosities ofsemi-fluid polymers, intermediate crosslink densities transform gummypolymers into materials that have elastomeric properties and potentiallyhigh strengths, and highly crosslink densities can cause materials tobecome rigid, glassy and even brittle. The crosslink density of thecured polymer, which in the case of the present invention constitutesthe colorants-containing elastic film, stems primarily from theconcentration of the crosslinking agent in the pre-polymerizationmixture, which in the case of the present invention constitute the inkcomposition once all its parts are adjoined on the substrate.

Hence, according to some embodiments of the present invention, the levelof crosslink density of the cured ink composition is an intermediatelevel which affords a highly pliable, stretchable and elastic film.

The type of crosslinking agent also influences the level of crosslinkdensity, whereas the chemistry of the crosslinking reactions determinesthe strength and frequency (density) thereof. However, a substantialfactor that affects the choice of a crosslinking agent is its chemicalmechanism of action and the type of by-products which are emitted duringthe polymerization, crosslinking and/or curing reactions.

For example, some of the most prevalent and industrially usedcrosslinking agents in the general polymer and inkjet specificindustries are amino resins, or polyamines, such asmelamine-formaldehyde resins. Other families of widely used crosslinkingagents include the methylated melamine family, the methylated high iminomelamine family, the highly alkylated mixed ether melamine family, thehighly n-butylated melamine family, the highly alkylated urea family,the partially iso-butylated urea family, the benzoguanamine family andthe glycoluril family.

Amino resins are thermosetting plastics formed from the reaction offormaldehyde and an amino group on a polyamine compound such as urea ormelamine. They are used per-se as bonding agents in plywood and particleboard and wrinkle-resistance agents in textiles. They are also moldedfor electrical devices and various commercial and home applications, andused in paper towels and textile finishing to increase water resistance.In the context of embodiments of the present invention, amino resins areused primarily as crosslinking agents, with melamine-formaldehyde resin(MFR) as an exemplary representative of this group.

Listed below are some additional exemplary crosslinking agents from theamino/formaldehyde resin family.

Methylated melamine crosslinking agents react by general acid catalysiswith a high tendency for self-condensation reactions that improve thereaction speed but limit the flexibility of the cured films. Exemplarycommercially available members of this group include CYMEL® 301, CYMEL303 ULF, CYMEL 350 and CYMEL 3745.

Methylated high imino melamine crosslinking agents exhibit low methyloland a high imino content and can be described as oligomeric in naturewith methoxymethyl and imino as main reactive functionalities. Thesereagents react according to general acid catalysis with a high tendencytowards self-condensation reactions that improve the polymerizationreaction speed but limit the flexibility of the cured films. Exemplarycommercially available members of this group include CYMEL® 323, CYMEL325, CYMEL 327 and CYMEL 328.

Highly alkylated mixed ether melamine crosslinking agents are monomericin nature with alkoxymethyl as the main functionality. These agentsreact according to specific acid catalysis with a low tendency forself-condensation that enhances the flexibility of the cured film.Exemplary commercially available members of this group include CYMEL®1116, CYMEL 1130 and CYMEL 1133.

Highly n-butylated melamine crosslinking agents exhibit improvedadhesion to relatively unclean substrates than methylated melamineresins, and provide better intercoat adhesion and adhesion to metalsubstrates. Exemplary commercially available members of this groupinclude CYMEL® 1156 and CYMEL MB-98.

Highly alkylated urea crosslinking agents exhibit high solubility inpolar solvents and limited solubility in hydrocarbon solvents. Exemplarycommercially available members of this group include CYMEL® UM-15 andCYMEL-U-80.

Partially iso-butylated urea crosslinking agents exhibit highcompatibility with organic solvents and many polymer backbone resins,including epoxy resins. Exemplary commercially available members of thisgroup include CYMEL® U-646, CYMEL U-662, CYMEL UI-19-I and CYMELUI-19-IE.

Benzoguanamine crosslinking agents provides improved adhesion to metalsubstrates, with good chemical and detergent resistance properties,compared with melamine and urea crosslinking agents. Exemplarycommercially available members of this group include CYMEL®1123 andCYMEL 659.

Glycoluril crosslinking agents are used as high performance crosslinkingagents with improved properties over existing melamine andbenzoguanamine resins. These crosslinking agents differ primarily in thenature of their alkylation alcohols and consequently in theirhydrophobicity. Exemplary commercially available members of this groupinclude CYMEL 1170 and CYMEL 1172.

While the aforementioned amino resin crosslinking agents are effective,they contain between 1000 ppm up to 2.5% formaldehyde, and further emitmore formaldehyde during the crosslinking reaction.

The growing awareness among consumers, workers and manufacturers, haspushed the consumer-products market in general and the polymerindustries in particular to search for compositions and processes whichminimize of altogether nullify the use of harmful ingredients and theproduction of harmful by-products. One such by product is formaldehyde,which is a bi-product emitted during the polymerization and curingprocess of polymers using crosslinking agents belonging to theaforementioned families.

These days, any textile ink containing formaldehyde is restricted foruse in certain applications, based on formaldehyde content of thegarment according to Oko-Tex Standard 100 (Oeko-Tex). Althoughformaldehyde, which forms upon use of amino resin crosslinking agents,may evaporate from the garment at high temperatures, the levels offormaldehyde can never reach the allowed values according to the widelyaccepted Öko-Tex Standard 1000.

Presently many manufacturers in the garment and consumer productindustries prefer to refrain from using ink compositions containing oremitting formaldehyde to protect their employees and customers fromexposure to formaldehyde.

To cater to this emerging need, the present inventors have studiedalternatives to the aforementioned crosslinking agents with theobjective of providing a water-based formaldehyde-free, pigmented inkfor direct print on garments. While reducing the present invention topractice, the inventors have successfully used different classes ofcrosslinking agents in the context of embodiments of the presentinvention, which do not use or emit formaldehyde, and can therefore beused as ink compositions in inkjet printing processes that comply withthe strictest standards of the industry. Hence, according to someembodiments of the present invention, a crosslinking agent which doesnot comprise or emit formaldehyde, is referred to herein as“formaldehyde-free crosslinking agent”.

One alternative family of formaldehyde-free crosslinking agents includesdialdehydes, other polyaldehydes or dialdehyde acid analogues having atleast one aldehyde group, such as, for example, C₂-C₈ dialdehydes. Awidely used dialdehyde, which is used in diapers, is the shortestdialdehyde glyoxal. U.S. Pat. Nos. 4,285,690, 4,345,063 and 4,888,093describe alkylated glyoxal/cyclic urea condensates that serve ascrosslinkers for cellulosic fibers for high water retention pads. Anon-limiting example of such crosslinking agents includes glyoxal.

Another alternative family of formaldehyde-free crosslinking agentsincludes heteroaryl polycarbamate crosslinking agents which are based ona moiety derived from the group consisting of linear or cyclic ureas,cyanuric acid, substituted cyanuric acids, linear or cyclic amides,glycolurils, hydantoins, linear or cyclic carbamates and mixturesthereof. Exemplary crosslinking agents that belong to this family andare suitable in the context of crosslinker agents suitable forcrosslinking the ink composition to cellulosic fabrics according to someembodiments of the present invention, are disclosed, for example, inU.S. Pat. Nos. 6,063,922, 5,596,047 and 7,381,347 and U.S. PatentApplication No. 20040116558. A non-limiting example of such crosslinkingagents includes CYLINK®2000 by Cytec Technology Corp.

Another alternative family of formaldehyde-free crosslinking agents isbased on diacetone acrylamide/hydrazine (polyalkenyl ether resins).These crosslinking agents, some of which are commercially available, aredisclosed in, for example, in U.S. Pat. Nos. 5,348,997, 5,432,229 and7,119,160. A non-limiting example of such crosslinking agents includesN-(1,1-dimethyl-3-oxobutyl)-acrylamide (DAAM)/hydrazine by Kyowa HakkoChemical Co., Ltd., Japan.

Another alternative family of formaldehyde-free crosslinking agents isbased on carbodiimides. The term “carbodiimide” refers to the functionalgroup having of the formula —[N═C═N]_(n)— which can react readily withamine and carboxyl groups. Carbodiimide crosslinking agents aredisclosed in, for example, in Japanese Patent Application Kokai(Laid-Open) No. 187029/1984, U.S. Patent Application No. 20070148128,U.S. Pat. Nos. 5,360,933, 6,124,398 and 7,425,062 and EP0277361. Anon-limiting example of such crosslinking agents includes CARBODILITE®by Nashinbo, Japan.

Exemplary ink compositions comprising formaldehyde-free crosslinkingagents, according to some embodiments of the present, have been preparedand successfully used, as demonstrated in the Examples section thatfollows hereinbelow.

The ink composition optionally contain one or more other ingredientsaccording to some embodiments of the present invention, such as, forexample, surfactants, humectants, wetting agents, binders,buffering/neutralizing agents, adhesion promoters, bactericides,fungicides, algicides, sequestering agents, softeners, thickeners,anti-foaming agents, corrosion inhibitors, light stabilizers, anti-curlagents, thickeners, non-reactive agents, softeners/plasticizers,specialized dispersing agents, specialized surface active agents,irradiation sensitive agents, conductivity agents (ionizable materials)and/or other additives and adjuvants well-known in the relevant art.

Humectants are typically used for adjusting surface tension andviscosity as well as for avoiding nozzle blockage due to formation of adried film. These include, without limitation, polyethylene glycol andother polyalcohol mixtures.

Non-limiting examples of anti-foaming agents (defoamer) include BYK 024,BYK 012; BYK 31 (commercially available from Byk-Chemie), FOAMEX 810,AIREX 901, AIREX 902 (commercially available from Evonik Tego ChemieGmbH, Essen, Germany), SURFYNOL DF 37, SURFYNOL DF 210, SURFYNOL DF 75(commercially available from Air Products Ltd.), and more.

Non-limiting examples wetting agents include BYK 307, BYK 348 and BYK3410 (commercially available from Byk-Chemie), TWIN 4000, WET 260 andWET 510 (commercially available from Evonik Tego Chemie GmbH, Essen,Germany), and more.

Exemplary softeners/plasticizers include, without limitation, an adipateester, a phthalate ester, an aryl phosphate, a trimellitate ester and aplastisol, and many other commercially available softeners/plasticizerswhich are offered by such companies as ExxonMobil, Morflex andByk-Chemie. The content of the softener/plasticizer ranges from about0.01 weight percentage to 2.5 weight percentages of the total weight ofthe ink composition.

Exemplary surface active agents include, without limitation, soap, adetergent, a syndet, an emulsifier, an anti-foaming agent, apolyalkylsiloxane, an anionic surface active agent, a cationic surfaceactive agent and a non-ionic surface active agent. The content of thesurface active agent ranges from about 0.01 weight percentage to about 5weight percentages of the total weight of the ink composition.

An exemplary buffering agent is tris(hydroxymethyl aminomethan).

Following are exemplary general formulation for each of the parts of theink composition according to some embodiments of the present invention.

Exemplary formulations of the first part (the immobilization part),according to some embodiments are based on the following percentage ofcontent and attribute ranges:

A property-adjusting agent    4-20%; A proto-elastomeric binder   0-40%; (optional) Humectants   45-55%; Neutralizing/buffering agent  1-4%; Anti-corrosion agent for iron 0.1-2%; Copper/Aluminum 0.1-2% anti corrosive agent Other additives  0-5%; Deionized water to 100%;Viscosity at 34° C. 9-12 cp; pH 4.2-5.0; and Surface tension 25-40 N/m.

The property-adjusting agent can be, for example, a transitory organicacid acting as a pH-adjusting agent. In such cases, the organic acidcontent in the immobilization part ranges from 4% to 20%, and the watercontent of the immobilization part ranges respectively to the content ofthe acid.

For another example, since it was found that some proto-elastomericfilm-forming agents are stable in the presence of an acid but congealupon the addition of a metal oxide, the acid will be added to theformulation containing the colorant, and the property-adjusting agentcan be transparent nano-titania, acting as a first metal oxide, or ametal ion complexing agent. In these cases, the nano-titania content inthe immobilization part ranges from 10% to 15%, and the water content ofthe immobilization part ranges respectively to the content of the metaloxide.

Other examples of property-adjusting agents and volatile agents includeisopropanol (20-40%), acetone and/or hydroxyl acetone (20-40%).

The optional proto-elastomeric binder (which is not property-sensitive)may be an acrylic emulsion, styrene acrylic emulsion, urethane emulsion,PVP or PVA included in the formulation in an amount of 4-40% to achievebetter adherence of the pigments and also to assist in flattening theloose fibers of a textile substrate.

According to some embodiments, in cases where the property-adjustingagent is a transitory organic acid it is present in the formulation ofthe first part in 6-12%, a proto-elastomeric acrylic binder is presentin about 5-15% humectants 10-30% and deionized water make up to 100%.The organic acid is a volatile organic (formic acid or acetic acid) acidsuch as lactic, glycolic or propionic acid (otherwise transitory), withthe latter used in the Examples section below as a suitable odorless andtransitory organic acid.

Following the exemplary first part, an exemplary and correspondingformulation of the second part of the ink composition (the colored part)is based on the following percentage of content ranges:

A colorant mixture 10-20% Property-sensitive proto-  25-30%; elastomericfilm forming agent Tg of the film-forming agent −35 to 0° C. A firstmetal oxide (optional 10-20% if using a third metal oxide) Humectants(glycol mixture)  20-40%; Amino resin crosslinking agent  2-4%;Bactericide/Fungicide 0.1-1%;  Blocked acid catalyst   1-1.5%;Neutralizing/buffering agent  0.2-0.6%; Defoamer  0.1-0.6%; Wettingagent/surfactant 0.1-2%;  Organic solvent  0-5%; Other additives  0-2%;Deionized water to 100%; Viscosity at 34° C. 10-13 cp; pH  8-8.5; andSurface tension 25-36 N/m.

An amino resin crosslinking agent, such as melamine or urea resin, or aformaldehyde-free crosslinking agent, according to some embodiments ofthe present invention, can be used as a crosslinking agent.

The colorant is typically a dispersion of 20% pigment in water and asuitable dispersant. The viscosity is measured for shear force range at1-4000 sec⁻¹.

The second part of the ink composition may be buffered to be alkaline(basic) or neutral, so as to maintain the property-sensitive agent inits emulsified form.

The third part of the ink composition (the underbase part) is similar tothe formulation of the second part with some variations with respect tothe dispersant, the pigment and the proto-elastomeric binder whichtogether can be regarded as a property-sensitive proto-elastomericfilm-forming system, and is therefore based on the following percentageof content ranges:

Second metal oxide (acting 15-20% also as colorant) Property-sensitiveproto- 25-45% elastomeric film-forming agent Proto-elastomeric film-15-25% forming agent (optional) Tg of the film-forming agent(s) −35 to−0° C. Dispersant 1-6% Bacteriocide/Fungicide  0.1-0.5%; Humectants 30-45%; Defoamer  0.2-0.4%; Neutralizing agent  0.1-0.2%; Wettingagent/surfactant  0.1-0.5%; Organic solvent  0-5%; Other additives 0-10%; Deionized water to 100%; Viscosity at 34° C. 12-14 cp; pH 8-8.5;and Surface tension 25-36 N/m.

The ink compositions, according to embodiments of the present invention,are utilized most effectively by a unique process as presented indetails hereinbelow. The process presented herein was practicedsuccessfully with outstanding results, as demonstrated in the Examplessection that follows.

Since the immobilization effect occurs instantaneously upon contactbetween the first and the second or third parts, each of the parts ofthe multi-parts ink composition should be dispensed and jetted fromcompletely separated and designated printhead systems, so as to preventpremature immobilization of the ink composition and keep itsubstantially liquid at all steps of the process before curing, at leastup to the point where the composition is positioned desirably on thesurface of the substrate.

Hence, according to one aspect of embodiments of the present invention,there is provided a process of printing an image on a stretchable and/orflexible substrate. The process, according to some embodiments of thepresent invention, is effected by digitally applying, by means of aplurality of inkjet printheads, onto at least a portion of a surface ofthe substrate, the multi-part ink composition presented herein, which isformulated to be suitable for use in inkjet printheads.

As presented hereinabove the ink composition includes a first part,applied by at least one first printhead, and a second part applied by atleast one second printhead, namely each part is jetted from one or moredifferent designated printheads, wherein the first part includes aproperty-adjusting agent, and the second part includes aproperty-sensitive proto-elastomeric film-forming agent and a colorant,whereas a time interval between the application of the first part andthe application of the second part is less than 1 second, therebyforming the image in a form of an elastic film attached to a surface ofthe substrate on the substrate.

The printing process is designed and programmed such that the variousparts of the ink composition will be applied concomitantly (oressentially simultaneously) on the surface of the substrate by adigitally controlled precise mechanism, and that every drop in thecolor/pigment-containing parts of the ink composition (second, third andfourth) will come in contact with at least a drop of the immobilization(first) part.

The term “concomitantly”, as used herein, refers to the timing of one ormore occurrences which take place concurrently, or almost concurrently,namely within a short time interval. According to embodiments of thepresent invention, this short time interval is less than one second,less than 3 seconds, less than 5 seconds or less than 10 seconds.

The process, according to embodiments of the present invention, is basedon the use of multi-components (parts) ink compositions, wherein all ofthe components (parts) are formulated and selected to be suitable alsofor the main inkjet printing techniques, such as the “drop-on-demand”technique and the likes, as these techniques are familiar to any artisanskilled in the art. Therefore, according to embodiments of the presentinvention, the ink composition used in the processes presented herein isfor use in an inkjet printing machine, wherein each part of amulti-parts ink composition is applied (jetted, printed) from at leastone different designated printhead.

The process presented herein is directed at a typical inkjet technique,as known in the art, which is performed using standard or proprietaryprintheads and other printing machinery.

Since each of the various parts of the ink composition used in theprocess presented herein is jetted by a digitally-control manner, theareas onto which each part is applied can essentially overlap, coveringsubstantially the same area of the image (coextensive areas). Inparticular, the first part of the ink composition, which is essentiallycolorless and transparent in some embodiments, is applied onto thesurface as a silhouette of the image, namely as a solid outline andfeatureless interior of the image. This effect further contributes tothe reduction in the amount needed to effect immobilization of the inkcomposition, as the first part does not form extending marginsperipheral to the image. This effect also widens the scope of suitablesubstances which can be used to formulate the immobilization part, asstaining of unprinted areas of the substrate which are not covered bycolorants, is no longer a problem.

While reducing the present invention to practice, it was observed that adroplet of any part of the multi-part liquid ink composition, accordingto some embodiments, is absorbed by a 100% cotton fabric over a timeperiod that ranges from about 20 seconds to 5 minutes, depending onwetting properties of the various parts. This time rage for soaking in100% cotton fabric was observed also for tap water. When syntheticcomponents are blended into the fabric, the fabric becomes less wettableand the absorption (soaking) time increases. The process settings andresults also depend on the finish of the fabric.

One factor that accomplishes satisfactory immobilization is the speed atwhich the congelation is accomplish. It is accomplish best when a singledroplet of any of the pigment-containing parts of the multi-parts inkcomposition (opaque or colored parts) comes in contact with a droplet(one droplet of the immobilization part can affect more the one coloreddroplets) of the immobilization part prior to accumulation of manyadditional droplets of any part. The time (speed) factor may determineif a large drop is formed or not, taking into account that larger dropsmay soak faster into the substrate in cases of absorptive substrates, orcoalesce (joining with other droplets) as a result of partial dewetting,leading to the formation of non-uniform and poor coverage of anon-absorptive substrate.

The process presented herein, according to some embodiments thereof, iseffected by applying all the various parts of the multi-parts inkcomposition by means of separate inkjet printheads concurrently,substantially concomitantly, or very near concomitant applicationthereof, namely at a time gap or interval that is shorter than about1-10 seconds between the time a droplet of a part containing aproperty-adjusting agent or property-sensitive proto-elastomericfilm-forming agent contacts the substrate, and the time a droplet of thecounterpart component contacts the same region of the substrate.According to some embodiments of the present invention, this timeinterval can be shorter than 0.75 second, shorter than 0.50 seconds andeven shorter than 0.25 seconds.

Another factor which governs the wicking of a liquid droplet into anabsorptive substrate is the size of the droplet. A small andlight-weight droplet will tend to stay atop the surface rather than besmear and soaked into it. Small drop-size is also advantageous in caseof an impervious/impregnable substrate, as small drops are less prone tospreading and smearing. Hence, according to some embodiments of thepresent invention, the average jetted drop volume of each of the partsof the ink composition ranges independently from 50 pico liter to 100pico liter (pL). At this size, the plurality of jetted droplets,stipulating they are discreet, are small enough to stay atop the surfacebut large enough to flatten loose and protruding fibers of textilesubstrates. Being substantially small and spaced not too densely priorto the congelation reaction between the droplets of thepigment-containing parts and the droplets of the immobilization part, aplurality of such droplets can cover an area without compromising on itscoverage and its newly-applied color perception.

Exemplary substrates of flexible absorptive materials include, withoutlimitation, paper, cardboard, textile fabrics, cloths and garments ofall sorts and types including woven and non-woven materials and fabrics.

Exemplary substrates of stretchable and flexible absorptive materialsinclude, without limitation, cellulosic or synthetic textile fabrics,cloths and garments of all sorts and types including knitted, woven andnon-woven materials and fabrics.

Exemplary substrates of flexible non-absorptive materials include,without limitation, soft signage media and other composite syntheticimpervious materials, laminated, coated and plasticized surfaces ofvarious materials, as well as other substrates which are substantiallyimpregnable to liquids, such as high surface tension and impervioussubstrates that do not interact with a liquid ink composition so as torestrict the movement of the jetted droplets, including metal foil,plastic and other natural and man-made flexible polymeric materials.

The term “surface”, as used herein, refers to the exterior or upperboundary, the external part or layer or the outward appearance of asubstrate. This term is also used to describe any area of a surface,including specific parts of the surface. According to embodiments of thepresent invention, the image can be printed on at least a portion of thesurface, as required by the design of the image.

According to the present invention, textile fabrics may include wool,silk, cotton, linen, hemp, ramie, jute, acetate fabric, acrylic fabric,LASTEX™, nylon, polyester, rayon, viscose, spandex, metallic composite,carbon or carbonized composite, and any combination thereof. Accordingto some embodiments, the substrate onto which the image in printed on isa garment made of a textile fabric, and according to other embodimentsit is comprised substantially of cotton.

The surface described above may form a part of an object that is made ofthe same material or, alternatively, of an object that includes one ormore additional stretchable and/or flexible layers such as, for example,a paper layer, a foam layer, a textile fabric layer, a natural orsynthetic rubber layer, a metal foil layer, a resin layer and the likes,and any combination thereof.

In general the surface can be of all materials and combinations ofvarious materials, which are designed for a variety of applications,including printed commercial objects, sales promotion items, printedtextiles, T-shirts, accessories, knitted, woven and non-woven materials,apparel, home furnishings, gaming table covers, flags and banners, softsignage, and trade show displays.

The process, according to some embodiments of the present invention, issuitable for inkjet printing a color image on a surface of any color orshade within the color range. In general, a conventional inkjet printingon any surface involves the visual blending of colorants in a form of aparticular mix of different colorants on the printed surface. In thejargon of the art, a “process colorant” is substantially transparent anda “spot colorant” is substantially opaque. Spot colorant can be jettedlike process colorants, and are typically used on top of processcolorants in order to afford highlights and emphases over the imageusually in pre-defined coloration.

As further discussed hereinabove, ink-jet printing of high-quality andhigh-resolution is based on placing very small dots of several basiccolors in proximity so as to create a spectrum of colors from the visual(perceived) mixing of these basic colors. Each location of the image maybe a unique blend of basic colorants constituting a unique color. Thus,the transparency of the ink is crucial for creating the spectrum asincident and substantially “white light” is filtered through the basiccolors mix and reflected as a colored light back to the observer. Thereflection of the light depends on the absorption of the backgroundsurface, hence on its color, and therefore non-white surfaces do notreflect all colors and as a result the ink or ink mixes forming theprinted image are not perceived in their intended colors.

Thus, the key limitation in printing substantially transparent liquidink compositions on any non-white surface, and especially on darklycolored or transparent surfaces, stems from the inability of thenon-white surface to reflect white light from the surface back throughthe applied transparent ink and to the eye of the observer, whichrenders the image dull, dark and color-skewed. Therefore presently knownprinting technologies are limited when applied on darkly colored orotherwise non-white surfaces.

In cases where the surface is a dark surface, the process may employ theuse of a third part of the ink composition such that can form a lightlycolored or white opaque underbase (background) for the colored image.The third part is applied (jetted) from at least one printhead referredto as a third printhead, designated to apply the opaque andlightly-colored pigment.

As in the case of the second part of the ink composition (the coloredpart), the third part (the white opaque underbase part or the opaqueunderbase part), is applied as a silhouette of the image, not extendingoutside its outline, unless a particular part of the image is defined aswhite.

The second part (colored part), which typically includes 4 processcolors and spot colors, is formulated to have a lower ratio ofstretchability since it is typically applied on-top of a white(lightly-colored) substrate or over the white (lightly-colored) opaqueunderbase layer.

According to some embodiments of the present invention, the applicationof each of the parts of the ink composition is effected concomitantly;as exact simultaneous application is not possible (only one printheadcan be positioned over any given point of the substrate at any givenpoint in time). However, in typical inkjet machines, and particularly inwide-format inkjet printers, the image is formed in a series of passes,or strips, applied in a predetermined sequence so as to optimize thetime it takes to cover the entire printed area at a minimal time andnumber of passes.

Hence, according to some embodiments of the present invention, theapplication of the first (immobilization) part precedes the applicationof each of the second and third parts. According to other embodiments,since the immobilization part is effective also when applied shortlyafter the other parts, the application of the third part may precede theapplication the first and second parts. According to yet otherembodiments, where a third (underbase) part is not used, for instance ona white substrate, the application of the first and second parts can besubstantially concomitant, namely there is no significant difference inthe final result if one of the first or second parts reaches the surfacebefore the other at a minute time difference ranging from 0 to 1seconds. This is also the case when the first and third parts arerelevant, namely as long as the top layer is the colored part is appliedon top of layers of either the first or the third part, the final resultis the same desirable result.

According to some embodiments of the present invention, the first partis applied concomitantly with both the third and the second parts,namely the first and third parts (immobilization part and opaqueunderbase part respectively) are applied in the first pass, followedshortly thereafter, in less than a second, with a pass wherein the firstpart is applied concomitantly with the second part (immobilization andcolored parts). According to these embodiments, the immobilization partis applied in both passes, once concomitantly with the white background,and again concomitantly with the process colors.

Alternatively, the printing process is effected by applying two completelayers, namely one layer comprising the opaque underbase part, which isprinted in its entirety before the following layer of the colored partof the ink composition (comprising CMYK colorants and the likes) whichis applied thereon. In these embodiments the immobilization part isapplied concomitantly with the (white) opaque underbase part, and thenan additional portion of the immobilization part may be appliedconcomitantly with the colored (CMYK) part of the ink composition.

As in typical inkjet process, the colors are jetted in amounts whichcorrelate to the type of substrate, its color and the desired colorintensity and coverage in each given segment of the image. Increasingcolor intensity can be afforded by increasing the drop density per unitarea. The drop density output of a given printhead (namely withoutchanging the type of printhead) per unit area, can be increased byincreasing the number of passes of the printhead(s) over the area and/orincreasing the number of printheads jetting the same fluid. In order toprovide an effective underbase for color images printed ondarkly-colored substrates, the jetted amount of the underbase part istypically larger than the jetted amount of the colored part(s) of theink composition, as high as 5-fold respectively. However, as presentedhereinbelow, the amount of the underbase part needed to be applied on adark stretchable substrate can be reduced dramatically if pre-wettedwith simple tap water or another wetting solution and then wiped with asqueegee prior to applying the underbase part, as described in U.S.Provisional Patent Application No. 61/245,333, filed Sep. 24, 2009, andin a U.S. Patent Application by the present assignee, titled “A DIGITALPRINTING DEVICE WITH IMPROVED PRE-PRINTING TEXTILE SURFACE TREATMENT”,and having Attorney's Docket No. 48770 which is co-filed with theinstant application and incorporated in its entirety as fully set forthherein.

Since all the parts of the multi-part ink composition can be applied onthe substrate by means of printheads which jet very small droplets ofliquids at a controllable rate, one of the advantages of the processpresented herein, is a considerable reduction in the total amount ofapplied liquids which are required to form a vivid and durable image ofthe substrate, a factor that translates directly into reduced drying andcuring times, leading to a great reduction in energy costs.

Specifically, the process presented herein greatly reduces by at leastone order of magnitude the jetted amount of the first part(immobilization part) of the ink composition, which is somewhatcomparable to the wetting composition discussed hereinabove. Thereduction in the amount of the applied immobilization part and thereduction in the duration of the process also reduced the overall costof ink-ingredients, and afforded a process which is less hazardous tothe environment and more suitable for use in inkjet technology. This isparticularly effective in the use of the immobilization part of the inkcomposition, which can now be used sparingly, avoiding staining of thegarment around the image and saving primarily on drying energy and time.

It was further found that the relative low volume application of theimmobilization part of the ink composition is sometimes advantageous ifthe printing mode is, for example, a “one pass” mode, such as in “rollto roll” print. In such mode the immobilization part is appliedcontinuously at short a distance ahead of the color print front. In suchembodiments, massive spray of the immobilization part is non-feasibledue to the risk of clogging, the volumes which are evaporated thereafterand other ill effects.

Hence, according to some embodiments of the present invention, theamount of the first part of the ink composition, which is jetted in theprocess presented herein in order to achieve over 100% coverage of thesurface, ranges from about 0.005 grams per square inch (g/int) to about0.040 grams per square inch. In comparison, the wetting composition,disclosed in IL Patent No. 162231 and WO 2005/115089, is applied in anamount of about 0.07-13 grams per square inch, and preferably of about0.7-4 grams per square inch.

Another advantage of lowering the amount of the immobilization partneeded to exert the desired immobilization effect, is the ability toapply more of the second (colored) part of the ink composition, comparedto the amount of the second part which can be applied in otherprocesses, such as processes using a wetting composition. The optionalincrease in amounts of the colored part is enabled by increase inresolution or optional multi-pass of the printheads as the ratio ofcolored part to immobilization part is kept substantially constant. Theability to apply more of the colored part has a remarkable positiveeffect on the overall quality of the resulting image in terms of colordepth and vividness.

Hence, according to some embodiments of the present invention, theamount of the second part of the ink composition, which is jetted in theprocess presented herein in order to achieve about 100% coverage of thesurface, ranges from about 0.015 grams per square inch (g/int) to about0.085 grams per square inch. In comparison, the maximal amount of thecolored part which could be applied on top of the wetting composition,disclosed in IL Patent No. 162231 and WO 2005/115089, was only about0.030 grams per square inch.

It is noted herein that the fourth part of the ink composition, which isan opaque and colored ink part, providing “spot colorant” inks tovarious regions of the image, is regarded and treated similarly as thesecond part of the ink composition, except for the appearance of each,the second part contains transparent ingredients and the fourth partcontains opaque ingredients. Hence throughout the discussion of theprocess of printing, the second part and the fourth part are synonymousin terms of amounts and order of jetting with respect to the first part(immobilization part) of the ink composition.

The third part (the opaque and typically white underbase layer) isapplied in an amount that would reflect the uneven (non-flat), and hencegreater surface area of some of the substrates for which the presentinvention is provided for. For example, the surface of a fabric exhibitsridges and grooves, and the white layer should fill these texturalfeatures in order to provide an evenly filled, continuous andstretchable layer for the colored part which will be applied thereon.Hence the amounts of the third part are typically higher than, andmostly double the amounts of the colored part.

The opaque (white) underbase part of the ink composition can be jettedby a plurality of printheads (3-4 printheads) so as to achieve a totalcoverage of up to than 400% on the surface by applying about 0.08-0.15grams per square inch of the underbase opaque part. For comparison, eachprinthead which applies one of the CMYK colorants of the colored part ofthe ink composition can apply about 0.024 (100%) grams per square inch,therefore assuming a total coverage of 140% by all four CMYK colors overthe underbase opaque part, the total amount jetted of the coloredtransparent parts of the ink composition is about 0.032 grams per squareinch.

According to some embodiments of the present invention, the jettedamount of the third (underbase) part ranges from about 0.07 grams persquare inch to about 0.15 grams per square inch.

For another example, in cases where an underbase opaque part is used,the immobilization part of the ink composition can be applied in twopasses, one at a rate of about 0.032 grams per square inch concomitantlywith the underbase opaque part, and at a rate of about 0.007 grams persquare inch concomitantly with the colored part of the ink composition.Alternatively, the opaque white underbase part of the ink composition(the third part) that masks a darkly colored surface of a substrate witha white background, can be applied at 100% intensity by 3-4 designatedprintheads which jet a total of 0.15 grams of the third part per squareinch concomitantly with the application of the first (immobilization)part which is jetted by one or two designated printheads at a rate ofabout 0.02-0.04 grams per square inch, prior to the application of thecolored part which is also applied concomitantly with the first part,both at a rate of about 0.01-0.02 grams per square inch, thereby formingan image on a darkly colored substrate.

According to some embodiments, the jetted amount of any of the parts ofthe ink composition can be selected to achieve less than 100% coverage,and be proportional to the required intensity of each of the processcolors composing any given point of the computerized graphic image,namely proportional to the CMYK demand per pixel or per unit ofinformation which depicts a point in the image.

As discussed hereinabove, the flatness and smoothness of the surface,particularly that of a stretchable fabric substrate, is one of the maincontributors to the quality of the resulting ink-jetted image appliedthereon. This is fundamentally different that applying a similar imageon intrinsically smooth surfaces, such as paper. The grooves, valleysand ridges formed by the threads, even in non-woven fabrics, and theprotruding fibers, affect the image adversely.

While the immobilization reaction substantially prevents the absorptionof the jetted droplets, the typically non-planar surface of the garmentfabric poses a problem of relatively very large area coverage, as thefabric surface contains valleys and ridges in order of magnitude muchgreater then the jetted droplets.

This uneven microscopic surface of a fabric-like substrate leads touneven coverage thereof by the microscopic droplets which experiencerelative dramatic variations in the slope angles upon impact, at variouslocations of the surface. The uneven surface of a fabric-like substrateposes a particular problem when the fabric is non-white and the image isprinted using an ink composition having a third opaque underbase part.If applied on an uneven surface, the underbase part must be applied insuch amount that would fill-in and practically flatten the unevensurface; hence the underbase part must be applied on uneven surfaces atlarge amounts, leading to excessive usage of ink, energy and time.

While reducing the present invention to practice, it was observed thattemporary flattening or planarization of the surface of the substratewith respect to the jetted droplets can be achieved by spraying thefabric with tap water, which allows faultless coverage of the surface onthe sprayed areas with a layer of the multi-parts ink having an opaqueor colored part which are immobilized concomitantly with animmobilization part on the watered/sprayed areas.

As presented hereinbelow, wetting of the substrate with tap water, thusforming a temporary planar surface, dramatically reduces the amounts ofthe opaque underbase part to be applied. Therefore the amount of sprayedtap water depends on the smoothness and microscopic planarity of thereceiving substrate. The amount of the opaque underbase part may then beabout from about 0.01 grams per square inch to 0.09 grams per squareinch, and the immobilization part also decreases from about 0.01 gramsper square inch to about 0.03 grams per square inch.

While further reducing the present invention to practice, it wasobserved that in order to improve the smoothness of the wettedsubstrate's surface, and particularly substrates having protrudingfibers as an intrinsic feature of their substance and making, amechanical device such as a squeegee, “air knife” or any other form of aflat strip-shaped, blade-shaped or roller-shaped mechanical object maybe passed across the wetted surface so that apply pressure on the wettedsubstrate, thereby flattening these fibers and other protruding featurestherein that may cause uneven capturing of the ink droplets.

U.S. Provisional Patent Application No. 61/245,333, filed Sep. 24, 2009,and in a U.S. Patent Application by the present assignee, titled “ADIGITAL PRINTING DEVICE WITH IMPROVED PRE-PRINTING TEXTILE SURFACETREATMENT”, and having Attorney's Docket No. 48770 which is co-filedwith the instant application and incorporated in its entirety as fullyset forth herein, teaches a digital printing machine for printingtextiles, such as fabric woven within a plane and comprising fibersextending outwardly from that plane. The machine according to thisapplication, includes a wetting unit for wetting the fabric to beprinted prior to the digital inkjet printing, a printing head for inkjetprinting on the substrate, and a flattening unit for exerting pressureon the surface of the substrate in order to flatten any outwardlyextending (protruding) fibers to the surface after wetting and beforeprinting. This flattening device and action thereby causes theprotruding fibers to stick to the surface of the substrate and tono-longer protrude, and thereby smoothing the substrate for inkjetprinting.

Using the aforementioned fiber-flattening device can be effected byspraying and wetting the substrate with plain tap water or anotherwetting composition, as disclosed therein. Tap water leave no stains orcause no color migration, leaching or fading, and hence can be used insome relative excess with respect to the parts of the multi-part inkcomposition provided herein. The application of the water need not beaccurate with respect to the area covered by the image and can exceed itif necessary. Thus, according to some embodiments of the presentinvention, the mount of tap water sprayed over the substrate is fromabout 0.4 to about 2 grams per square inch.

The resulting image, according to the present invention is unique in thesense that it combines qualities which are absent or lacking in imageswhich are printed by using presently known ink compositions and printingprocesses. The image afforded by the ink compositions provided herein,utilized in the process and devices provided herein can be distinguishedfrom other images ink-jet printed on stretchable dark or whitesubstrates.

Therefore, according to another aspect of the present invention there isprovided a substrate having an image printed on a stretchable and/orflexible surface thereon which is prepared by the printing process asdescribed hereinabove using a multi-part ink composition as describedhereinabove.

The image, according to this aspect of the present invention ischaracterized by an unusual and unique durability, resistance tomechanical, physical and chemical stresses, high wash-fastness,flexibility, stretchability and a pleasant hand-feel, and furthercharacterized by high color definition and depth, high resolutionphotorealistic qualities, even when applied to absorptive surfaces suchas lightly- or darkly-colored textile fabrics.

Reference is now made to FIG. 1 which is a schematic diagramillustrating a digital printing machine with a flattening unit accordingto embodiments of the present invention.

According to embodiments of the present invention, there is provided adigital printing machine 100 for printing textiles. The textiles maycomprise garments or other textile items made of fabric knitted and/orwoven within a plane, the fabric itself comprising fibers extendingoutwardly from the plain. The fabric may be based on any conventional orunconventional textile material. The fabric may for example comprisefelt, leather, fibrous materials, porous materials, materials havinghigh surface tension with the ink liquid, weaves of natural andsynthetic fibers, weaves of mixtures of natural and synthetic fibers,natural fibers including wool, cotton, linen and synthetic fibersincluding nylon or suede. The fabric is essentially planar with smallerfibers, hairs, extending outwardly from the plane. The machine comprisesa wetting unit 101 for wetting an item to be printed prior to printing.Wetting is performed for ink drop immobilization, thus limiting thepenetration of the ink into the depth of the fabric, which may causedull coloring of the garment, mixing of colors and blurring.

A printing head 103 prints on the item to be printed. A printing headcomprises at least one inkjet nozzle (not shown). The printing head canbe any conventional printing head, such as those marketed by Spectra,Inc., New Hampshire, USA, and others known in the industry.

When using conventional ink-jet type printing on textile without the useof the present embodiments, the outwardly extending fibers intercept thedrops from the nozzle before they arrive at their intended destinations,as discussed above.

Pressing or flattening unit 102 may be located between wetting unit 101and printing head 103, though other locations are possible. Pressing orflattening unit 102 exerts mechanical pressure on the item to be printedto flatten the outwardly extending fibers to the fabric after wettingand before printing. Flattening unit 102 may employ static pressure.Flattening unit 102 may be disengaged from the item to be printed (notshown) after flattening has been completed. The pressure of flatteningunit 102 on the fabric, after wetting and before printing, causes theextending fibers or hairs to bend back towards the fabric beforeprinting. The water from the wetting unit provides the fabric and thefibers with enough liquid to keep the outwardly extending fibers totemporarily remain stuck to the fabric. The fibers sticking to thefabric render the fabric as a smoother surface for printing without anyinterference of outwardly extending fibers.

Flattening unit 102 may be any construction that mechanically pressesthe fibers to the fabric as the fabric passes the unit. Flattening unit102 may be implemented using for example a downwardly pressing curtainsuch as a PVC curtain, a mechanical roller such as a metal or polymericroller, an Air knife, a squeegee, including for example a polymericsqueegee such as PVC or Natural or artificial rubber, silicon and, athin flexible metal squeegee, a brushing strip and the like. Flatteningunit 102 may replace the ironing unit (not shown), since there may be noneed to iron the fabric. Flattening unit 102 may be adjusted beforeflattening for achieving a desired level of pressure. For example,different types of fabric or different levels of wetting may requiredifferent levels of pressure. Such pressure adjustment may be performedby using a counter balance (not shown), adjustable mechanical spring(not shown) or by pneumatic pressure adjustment (not shown).

The item to be printed (not shown) may be a garment or any other fabric,such as leather or suede.

Printing head 103 comprises an array of inkjet nozzles for performingdigital printing. The inkjet nozzles may comprise a drop-on-demandpiezoelectric inkjet nozzle or a continuous piezoelectric inkjet nozzle.Additional heads may provide post-printing and may comprise, a curingunit for curing ink, an ironing unit for ironing the item to be printed,or a heat press. The curing unit may be an infrared curing unit, a hotair blowing curing unit or a microwave-curing unit. Printing machine 100may comprise an external head for stencil printing.

Printing machine 100 may comprise a printing table (not shown) forholding the items to be printed. Printing machine 100 may be a carousel,a matrix, or any other printing machine, as will be discussed in greaterdetail below.

Machine 100 may comprise additional printing heads and/or additionalflatting units and/or additional wetting units.

Machine 100 may comprise a controller for coordinating relative motionbetween the table assembly (not shown) and the flattening unit 102.

FIG. 2A is a schematic diagram of an exemplary printing machine with aroller-flattening unit. Printing machine 200 comprises a wetting unit201, a flattening unit 202, and a printing head 203. Flattening unit202, according to the exemplary diagram, is a roller, which is capableof exerting pressure on the item to be printed to flatten outwardlyextending fibers to the fabric after wetting and before printing. In theexemplary diagram, the flattening unit is located before the printinghead and after the wetting unit, though the units may be arranged in adifferent order.

FIG. 2B is a schematic diagram of an exemplary printing machine with apolymeric or metal curtain-flattening unit. Digital printing machine 300comprises a wetting unit 301, a flattening unit 302 and a printing head303. Flattening unit 302 comprises a polymeric, silicone, polyethyleneor metal curtain, which mechanically pushes downward on passing fabrics,thus exerting mechanical pressure on the item to be printed to flattenoutwardly extending fibers to the fabric after wetting and beforeprinting. In the exemplary diagram, the flattening unit is locatedbefore the printing head and after the wetting unit, though the unitsmay be arranged in a different order.

Reference is now made to FIG. 3, which is a schematic diagram of acarousel-printing machine 46 in which one of the stations 47 is awetting and flattening unit which includes a flattening unit 50according to an embodiment of the present invention. The garmentprinting apparatus 46 comprises other stations such as astencil-printing station 24, and digital printing station 25. Acombination of stencil printing and digital printing may be used forprinting a background color on the garment before performing the digitalprinting.

The wetting apparatus, which is part of digital printing station 47,comprises a wetting unit 48 comprising sprinklers and a tank part 49.The wetting unit may spray a wetting and immobilizing solution onto thetextile or garment.

In use, a garment is placed on one of a series of printing trays, whichgo around the carousel and stop at stations as needed. At each station,the printing trays go through the process being offered at that station.In the case of wetting and flattening unit 47, the garment undergoeswetting, and then is flattened using flattening unit 50 and then thetray is moved onwards to digital printing station 25 for printing whilestill wet and with the fibers still adhering.

In an embodiment, for each printed garment, the stencil printing, ifexecuted, is executed first, flash cured if required (not shown), thenthe wetting, then the flattening and then the digital printing. Theexecution of the stencil printing is optional and may be used forprinting background colors or standard images.

The digital printing can be performed at any application stage, whilefollowing the digital unit a flash cure unit may be used to dry thedigitally printed image.

FIG. 4 is a schematic drawing of a matrix-printing machine using aflattening unit, according to an embodiment of the present invention

Matrix 600 is a matrix of printing stations set out in linear manner sothat a garment is placed on a tray and passes down a row of stations tobe treated with a series of pre-printing, printing and post-printingfunctions. The matrix 600 features rail 601 which bears function head623 and function head 622, rail 602 which bears function head 621 andfunction head 620, rail 603 which bears function head 619 and functionhead 618, rail 604 which bears function head 617 and function head 616,rail 605 which bears function head 615 and function head 614 and rail606 which bears function head 612 and function head 613. Matrix 600 alsofeatures rail 608 which bears printing table (tray) 627, rail 609 whichbears printing table (tray) 626, rail 610 which bears printing table(tray) 625, and rail 611 which bears printing table (tray) 624.

In the exemplary diagram, function head 622 is a wetting head andfunction head 620 is a printing head. Flattening unit 628 is locatedbetween wetting head 622 and printing head 620 underneath rail 601. Inalternative embodiments, the units may be arranged in a different order.

Printing table 624, in the exemplary diagram, is first fed under wettingunit 622 for wetting the garment and then is fed under flattening unit628 while the garment is still wet, thereby causing the fibers to stickdue to surface tension. The table then passes to printing head 620,where digital printing takes place.

In the matrix, unit 622 could alternatively be a screen-printingstation, in which case the wetting and digital printing units would bemoved one station further along.

Reference is now made to FIG. 5, which is a schematic diagram showing aview from the side of a textile-printing machine according to thepresent embodiments. Printing machine 500 comprises a wetting unit 501,a roller type flattening unit 502, and a printing head 503. A garmentfirst passes the wetting unit 501, then is pressed when wet by theroller type flattening unit 502 and finally is printed under theprinting unit 503, while the area being printed is still wet from thewetting unit and the fibers around the textile material still adhere tothe underlying fabric.

FIG. 6 is a simplified flow chart illustrating an exemplary printingprocess for printing on a dark textile, using digital printing machinewith a flattening unit according to the present embodiments.

As discussed above, when printing on a dark garment, a white undercoatmay be printed on the garment prior to printing the image. In such acase, extensive wetting may be needed before printing the whiteundercoat. Thus, when printing an opaque layer, extensive wetting of thegarment is performed before printing the white undercoat. Referring nowto the drawing of FIG. 6, a process 700 of wetting, flattening andprinting is shown which is suitable for dark colored backgrounds. In box701, the garment is extensively wetted by a wetting unit in order tolimit absorption of the ink by the fiber. In box 702, a flattening unitexerts pressure on the item to be printed in order to flatten outwardlyextending fibers to the fabric after wetting and before printing. In box703, the opaque undercoat is printed. In box 704, digital printing ofthe image on the wetted opaque layer is carried out by expelling dropsof ink from nozzles of the printing head to desired points on thefabric, for example using the CMYK color system. Since the fibers of thefabric have been flattened and are clinging to the fabric surface, thefibers no longer intercept the ink drops and the drops thus land whereintended on the fabric, leading to sharper printing.

FIG. 7 is a schematic side view showing in greater detail an exemplarydigital printing machine comprising an exemplary flattening unit inoperative state. Digital printing machine 700 comprises chassis 704,scan axis 703 and flattening assembly 706. Scan axis 703 comprises arail which is placed on chassis 704 and provides the rail for bearingtray 705. Tray 705 is used for holding an item to be printed (notshown). The enlargement 706 shows in greater detail the assembly of theflattening unit. The exemplary flattening assembly comprises rigid arm707 which applies a constant pressure in the on state, elasticflattening unit 701 which may be made of rubber, wetting unit 702, ascounterweight 708, which is here shown as a variable counterbalance tothe weight applied by the rigid arm 707 to regulate the appliedpressure, and the reversible attachment unit 711 that attaches orseparates the flattening unit from the printing substrate.

Construction 710 holds the wetting spray units 702. Rigid arm 707 isattached to counterweight 708 which is here embodied as a variablecounterbalance. Regulated counterbalance 708 imposes a required level offlattening pressure on flattening unit 701. Reversible attachment unit711 comprises a piston that brings the flattening 701 squeegee intocontact with the printing substrate and detaches it after flattening.Counterbalance 708 regulates the pressure on the flattening unit topress against tray 705 for flattening and detaches the flattening unitfrom tray 705 after flattening and before printing. Arm 707 of theflattening unit is hinged in order to allow pressure regulation unit 708to regulate the weight applied to the garment. Attachment detachmentunit 711 may transfer the pressure to the flattening unit when switchedon. Adjusting the pressure on flattening unit 701 may be done forachieving a desired level of pressure. For example, different types offabric or different levels of wetting may require different levels ofpressure. Wetting unit 702 is used for wetting the item to be printed(not shown) before flattening. Wetting may be done, for example, byusing water or acid solution optionally composed with wetting additive.Flattening unit 701 is shown in operative mode flattening the item to beprinted (not shown) after wetting and before printing.

The item to be printed then passes under printing unit 709 to be printedwhile the fibers still adhere to the fabric.

FIG. 8 is a schematic side view of an exemplary digital printing machinecomprising the exemplary flattening unit of FIG. 7 in non-operatingstate. FIG. 8 comprises the same units that are described in FIG. 7. Bymeans of 711 piston the tension from counterweight 708 is released andflattening unit 701 and arm 707 are withdrawn from tray 705, and thusfrom the item to be printed (not shown). The garment etc is able totravel to the printing unit 709 to print on the item to be printed afterwetting and flattening.

FIG. 9 is a view of an exemplary flattening unit in operative state. Allunits shown in FIG. 9 are shown and described in FIG. 7. Flattening unit701 is operated by reversible attachment unit 711, for example apneumatic piston (on/off) that either attaches or separates 701flattening unit from the printed object, in order to press on the itemto be printed with the desired flattening pressure and to release asrequired.

FIG. 10 is a schematic view of the exemplary flattening unit of FIG. 9in non-operative state. All units shown in FIG. 10 are as shown anddescribed in FIG. 9. Flattening unit 701 and arm 707 are horizontal tothe tray (not shown) and are detached from the tray in order to enablethe printing unit (not shown) to print on the item to be printed afterwetting and flattening.

FIG. 11 is a close up view of the exemplary digital printing machine ofFIGS. 9 and 10 comprising an exemplary flattening unit in operativestate. Flattening unit 701 presses down on the item to be printed. FIG.11 shows also sprinklers 702 being used for wetting before flattening.

It is appreciated that certain features of the invention, which are, forclarity, described in the context of separate embodiments, may also beprovided in combination in a single embodiment. Conversely, variousfeatures of the invention, which are, for brevity, described in thecontext of a single embodiment, may also be provided separately or inany suitable subcombination or as suitable in any other describedembodiment of the invention. Certain features described in the contextof various embodiments are not to be considered essential features ofthose embodiments, unless the embodiment is inoperative without thoseelements.

Various embodiments and aspects of the present invention as delineatedhereinabove and as claimed in the claims section below find experimentalsupport in the following examples.

EXAMPLES

Reference is now made to the following examples, which together with theabove descriptions; illustrate the invention in a non limiting fashion.

General Printing Procedure:

The Examples below were executed on a “STORM” digital printing machine,manufactured by Kornit Digital Ltd., Israel, and equipped with a batteryof printheads, as described hereinabove, and a “squeegee” device asdescribed herein.

Printing frequency (the rate at which the digital data signals, 0 forclose or 1 for open, are transmitted to the printhead) of 10-20 KHz atresolution range of 363-727×363-727 dots per inch (dpi).

At these settings, one full printhead wide strip is printed in 4-8passes in order to obtain high resolution and over-coverage of thesubstrate. The distance between nozzles line in two adjacent printheadsis 25 mm, and 100 mm for two most distant printheads. At thisconfiguration the time between a pass applying one part of the inkcomposition and the time another part is jetted is about 0.02 secondsfor two adjacent printheads printing at 15 KHz and at 363 dpi, to 0.72seconds printing at 10 KHz and 727 dpi for the most remote positionedprintheads.

While reducing some of the embodiments of the present invention topractice, it was observed that the time taking for an aqueous based inkcomposition or a part thereof, such as the immobilization part, to soakinto the fabric after jetting, is well over 60 seconds. The soaking timefor an aqueous opaque white part of the ink composition is the shortest,as compared to the immobilization part and the colored parts, which isabout 20 seconds. Twenty seconds is the approximate minimal soaking timeof ink droplets which was measured on white cotton fabrics treateddifferently by various suppliers.

These observations are considered for the time of reaction between anytwo parts of the ink composition, which is almost instantaneous, isshorter by more then an order of magnitude then the time of soaking ofthe liquids into the substrate, ensuring that the immobilization of thedroplets is achieved before capillary action takes place.

The applied amount of each part of the ink composition should be suchthat a clear and vivid image is formed, without excess ink which leadsto smearing, prolonged drying and curing time and costly waste.

The amount of the part which is jetted first (not necessarily the “firstpart”) should flatten the protruding fibers in case of untreatedtextile. This effect will ensure that the next parts of the jetted inkcomposition that reach the substrate do not encounter perpendicularfibers that prevent the jetted droplet from reaching the surface of thesubstrate, and may be visible after drying over and around the outlineof the image and obscure or fuzz the printed image.

In an exemplary printing procedure, the opaque white underbase part ofthe ink composition is jetted by 3-4 printheads at a total amount ofabout 0.15 grams per square inch. Each of the CMYK pigments is jetted byseparate printheads, each printhead applying about 0.024 grams persquare inch, and assuming coverage of 140% by total 4 colors, the amountof jetted colored part is about 0.032 grams per square inch. Theimmobilization part of the ink composition is applied at a rate of about0.032 grams per square inch when immobilizing the opaque white underbaselayer, and 0.007 grams per square inch when immobilizing the coloredpart layers.

At the same time that the printed image is cured on the fabric byheat-activated catalysts (80-160° C.) which activate crosslinking agentsthat bind to functional groups in the substrate, all the carriers shouldbe evaporated from the substrate, preferably before the crosslinkingreaction begins. According to embodiments of the present invention, thetiming and duration of the curing stage can be easily optimized due tothe reduced total amount of applied ink composition in terms of totalliquids to be evaporated, which shortens the final drying time, ascompared to other printing techniques and particularly as compared tothe amount of liquids applied in other processes using a wettingcomposition with or without a property-adjusting or property-sensitiveagent(s). The reduced amount of applied liquids opens the possibility ofusing reagents of a lower evaporation rate. This also realizes a greatsaving and cost reduction of drying equipment and energy.

It is noted herein that elevated-temperature curing is optional when thepolymerization reaction can occur under 80° C. due to particularselection of certain ingredients such as polymerizationinitiators/catalysts, monomers/oligomers and/or crosslinking agents,such as photo-curable or radiation-curable ingredients.

Printing was typically performed on the surface of an untreated 100%white or black cotton T-shirt. Similar results were obtained when imageswere printed on a surface of 50% cotton and 50% polyester.

Untreated fabrics are fabrics which are used “as is” in the exact stateat which they are provided by the manufacturer. Specifically, when theterm “untreated” is used herein to describe fabrics and othersubstrates, it is meant to describe substrates for which no chemicalpreparation step was taken in order to render them ready for inkjetprinting other than placing the substrate in the printing machine.

It was also found that when printing on 100% polyester fabric, non-wovenmaterials, soft signage and other non-fibrous materials, theimmobilization part of the ink composition can be devoid of a bindersince the problem of protruding fibers does not exist.

Unless otherwise stated, the test printing was performed on a 100%cotton white T-shirts purchased from Anvil Ltd. or on a 100% cottonblack T-shirts (Beefy-T) purchased from Hanes. The T-shirts were used“as is”, or ironed for 5 seconds at 160° C. using an automatic press.All measurements of optical densities were performed on images whichwere printed on identical shirts (same production batch), printed atdifferent pretreatment modes.

The merits of the resulting multicolor image was assessed bothqualitative (visually inspected) and quantitative (numericallyparameterized). An exemplary multicolor standard-testing image wasprinted for a qualitative and quantitative assessment of the printingprocess and the resulting image.

The printing tests presented herein were conducted using a printingmachine equipped with a wetting apparatus and a fiber-flattening device,as disclosed in U.S. Provisional Patent Application No. 61/245,333,filed Sep. 24, 2009, and in a U.S. Patent Application by the presentassignee, titled “A DIGITAL PRINTING DEVICE WITH IMPROVED PRE-PRINTINGTEXTILE SURFACE TREATMENT”, and having Attorney's Docket No. 48770 whichis co-filed with the instant application. This machine allows for thewetting of the surface of the substrate, which is thereafter gentlypressed by a “squeegee” or a flattening device, causing any protrudingfibers to stick to the surface, and also temporarily fills grooves anddimples in the surface with a small amount of water or another wettingsolution, thereby affording a temporarily flattened and even substratesurface.

The white underbase part on black fabric was printed either directly ondark shirt without spraying the substrate with water, or on black fabricsprayed with tap water and flattened with a squeegee. When the fabricwas sprayed with tap water, the amount of the white underbase part ofthe ink composition required to reach a complete coverage of thedesignated area, was remarkably smaller than for print tasks ofidentical images and identical substrates but without the water andsqueegee treatments.

The standard-testing image included a pattern of squares, each squarerepresents a different combination of CMYK pigments (column-wise) anddifferent pigment dilution (row-wise), printed at a basic resolution of545×545 dpi, wherein the rows represent colored pigment dilution goingfrom 100% (undiluted) down to 10% in equal intervals of 10% plus a rowrepresenting dilution of the colored pigment to 5%, and further havingthree rows representing binary mixtures of Y+M, Y+C; C+M printedsimultaneously.

All prints were cured in hot air drier unit prior to analysis. Curingcycle was effected for 160 seconds at 140-160° C.

Example 1

The effect of the concomitant application of an immobilizing part and anopaque white underbase part of an ink composition, using the processaccording to some embodiments of the present invention, was demonstratedby printing a layer of an opaque white pigment directly on a blackT-shirt made of 100% cotton. Three tests were run, comparing the resultsof a single part white ink composition, a white ink composition printedon a black cloth after being wetted with a wetting composition asdisclosed in WO 2005/115089, and a two-part ink composition having animmobilization part and a white colored part.

The formulation and attributes of the first part of the ink composition(the immobilization part which contains the property-adjusting agent) ispresented below in Table 1, the wetting composition in Table 2 and thewhite colored part in Table 3.

TABLE 1 Immobilization Part Property-adjusting lactic acid   9% Ammonia(for buffering the acid)   3% A mixture of propylene glycol,   50%diethylene glycol, glycerin and/or other polyols (as humectants)Benzotriazole (as anti cupper 0.40% corrosion agent) Sodium nitrate (asanti corrosion 0.20% agent for ferrous metals) Acrylic emulsion   35%(film-forming binder) Appretan E 6200 (Tg −20° C.) Deionized water to 100% Viscosity at 34° C. 10 cp pH 4.7 Surface tension 37 N/m

TABLE 2 Wetting composition (Prior Art Formulation) Acetic acid (as a 2.5% transitory organic acid) BYK 348 (as a wetting agent) 0.15% Tapwater to  100% Viscosity at 34° C. 1-2 cp pH 2.5 Surface tension 31 N/m

TABLE 3 Opaque white underbase part Property sensitive film-formingacrylic emulsion  37% (Appretan E 6200, Tg −20° C.) Titania (as anopaque white pigment and second  18% metal oxide) A mixture of propyleneglycol, diethylene glycol  37% and glycerin (as humectants) TEGO 750(dispersant) 3.2% BYK 024 (as an anti-foaming agent) 0.2% Diethanolamine(as a buffering agent) 0.2% BYK 348 (as a wetting agent/surfactant) 0.1%Cymel 303 (amino resin crosslinking agent)   3% Nacure 2448 (a blockedacidic catalyst) 0.5% Acticide MBS (as a bacteriocide/fungicide) 0.1%Deionized water to 100% Viscosity at 34° C. (at shear force of 4000 13cp sec⁻¹) pH 8.5 Surface tension 34 N/m

FIGS. 12A-12B present color photographs of three untreated black 100%cotton textile pieces having a white opaque pigment part of an inkcomposition printed thereon by an inkjet printer. The printhead batterwas fitted with three dedicated printheads for white to ensure completecoverage and opacity on the black fabric, compared to a single printheadwhich is typically assigned for each of the CMYK pigments. Theprintheads were operated at a drop size of 75-85 picoliter, applied at0.335 grams per square inch and dada frequency of 12-20 KHz. The whiteink composition was printed in a pattern of 6 stripes each representinga different drop-density levels going from 100% to 50% in equalintervals of 10%.

FIG. 12A shows the results of printing the white pigment ink compositionprinted at a resolution of 636×636 dpi without any attempt to immobilizethe ink before curing, demonstrating unacceptable coverage of thesurface due to wicking of the white ink into the fabric before it hadcured. FIG. 12B shows the results of printing the white pigment inkcomposition at the same resolution after spraying the cloth with awetting composition based on acetic acid, demonstrating near acceptableresults which require additional applications of white ink in order tobecome acceptable. FIG. 12C shows the results of printing the inkcomposition, as an immobilization part (the first part) appliedconcomitantly with the opaque white pigment part (the third part) at aratio of 1:3 respectively and a resolution of 727×1000 dpi,demonstrating the superb results obtained when using the processpresented herein by an exemplary embodiment thereof.

As can be seen in Table 4 below, it has been observed that the amount ofan immobilization formulation required to afford an acceptable whiteunderbase suitable for color printing thereon can be decreased sharply,as compared to the amount of the comparable wetting composition.

Table 4 presents the amount in grams of either a sprayed wettingcomposition or a printed immobilization formulation, needed to affordcomparable immobilization of the colored ink on a black or white textilepiece, covering an area of 240×156 mm or 9.45×6.16 inches.

TABLE 4 Formulation Black textile White textile White Signage Wettingcomposition  29 grams   9 grams  5.4 grams Immobilization part 3.7 grams0.46 grams 0.32 grams

As can be seen in Table 4, the amount needed to immobilize colored inkon a fabric with the immobilization part is 13% of the amount of thewetting composition needed to stabilize the ink on black textile (about8-fold reduction in amount) and 5% of the amount on white textile (about20-fold reduction in amount). As can further be seen in Table 4, whenprinting on white soft signage (for more details on the substrate, seeExample 4 below), which is impregnable to liquids, the amount of therequired immobilization part is about 16-fold smaller that thecorresponding amount of wetting composition. Furthermore, since thewetting composition is sprayed on an area larger than the area of theimage, and the immobilization part is printed exactly under the image asits silhouette, the actual difference in the applied amount is actuallymuch greater, leaving no marks on the exposed (uncovered) substrate nearthe outline of the image.

Example 2

The effect of the concomitant application of an immobilizing part, anopaque white underbase part and a colored part of an ink composition,using the process described in Example 1 hereinabove, was demonstratedon a black T-shirt made of 100% cotton.

The formulations of the immobilization and underbase parts were the sameas presented in Example 1 hereinabove. The formulation of the coloredpart is presented in Table 5 below.

TABLE 5 Colored (CMYK) part Cabbojet 260 series (20% pigment in waterand   12% property-sensitive dispersant) Dispex A40 (asproperty-sensitive proto-  1-2% elastomeric film-forming acrylicdispersant) Acticide MBS (as bacteriocide/fungicide) 0.10% Propyleneglycol, diethylene glycol, glycerine   35% and mono-ethylene glycol(humectant) Cymel 303 (Melamine, amino resin crosslinking   3% agent)Nacure X49-110 (blocked acid catalyst)   1% Diethanolamine (bufferingagent) 0.40% BYK 031 (defoamer)  0.2% Proprietary acrylic emulsion (asproperty-   25% sensitive proto-elastomeric film-forming binder) BYK 348(surfactant) 0.10% Deionized water to 100% Viscosity at 34° C. (shearforce at 4000 10-13 cp sec⁻¹) pH 8-8.5 Surface tension 32-36 N/m

FIGS. 13A-13B present color photographs of two untreated black 100%cotton textile pieces having colored (cyan, magenta, yellow and black,or CMYK process pigments) ink compositions printed thereon in a patternof squares. Each square in the pattern represents a differentcombination of CMYK pigments (column-wise) and different drop-density(row-wise), printed at a basic resolution of 545×545 dpi on a whiteunderbase.

FIG. 13A shows the results when the colored pigments were printed on alayer of white ink applied at a rate of 0.32 grams per square inch,636×636 dpi resolution, 75-85 pL drop size and 12-15 KHz, after sprayingthe cloth with a wetting composition (as disclosed in WO 2005/115089)based on 2% acetic acid in tap water, showing an ordinary display ofcolor depth which is less than acceptable.

FIG. 13B shows the results obtained when using the process describedherein, where an immobilization part (first part) is printedconcomitantly with the colored pigments (second part), and less than asecond after an immobilization part (first part) was applied at a rateof 0.32 grams per square inch, 636×636 dpi resolution, 75-85 pL dropsize and 12-15 KHz, concomitantly with an opaque white pigment (thirdpart) using a third of the amount of white ink (0.11 grams per squareinch) to accomplish the acceptable results, demonstrating the superbresults obtained when using the inkjet printing process describedherein.

Example 3

The effect of the concomitant application of an immobilizing part, anopaque white underbase part and a colored part of an ink composition,using the process described herein, was demonstrated on a white T-shirtmade of 100% cotton.

The formulations of the immobilization, colored and underbase parts werethe same as presented in Examples 1 and 2 hereinabove.

FIGS. 14A-14C present color photographs of three untreated white 100%cotton textile pieces having colored pattern as printed on a blackfabric presented in Example 2 hereinabove.

FIG. 14A shows the results when the colored pigments were printed on thewhite fabric without any attempt to immobilize the ink before curing,showing a poor image with dull colors.

FIG. 14B shows the results when the colored pigments were printed afterspraying the cloth with a wetting composition (as disclosed in WO2005/115089) based on 2% acetic acid and 0.1% BYK 348 (used as a wettingagent) in tap water, showing mediocre results.

FIG. 14C shows the results obtained when using a process as describedherein, where an immobilization part (first part) is printedconcomitantly with the colored pigments (second part), demonstrating thesuperb results obtained when using the inkjet printing process presentedherein.

Example 4

Soft signage is a term used by artisans of the field to refer to printedsigns, banners, table covers, flags, trade show displays and the likes,wherein the printed media is made from fabric-reinforced syntheticpolymeric substrate. This term is therefore widely used to refer to themedia itself, namely soft and flexible plastic sheets that arereinforced with a network of fibers of loose mesh (gauze-like cloth).Soft signage substrates are typically impregnable to liquids and exhibita non-smooth texture imparted by the imbedded cloth, resembling that of“duct tape”.

Inkjet printing of soft signage poses a challenge due the tendency ofthe ink composition to smear and flow over the surface, particularlywhen used in excess on extensive areas, as required to overcome thedimpled surface texture and when printing large signs and banners. Theprocess described herein (in Example 1 hereinabove) was usedsuccessfully to print in color on media used for soft signage, aspresented in FIGS. 15A-15C.

FIGS. 15A-15C present color photographs of three white synthetic piecesthat serve as media for soft signage, namely a substrate for whiteformat prints. The figures show an image of a colored pattern (as shownin FIG. 13 hereinabove) printed thereon. FIG. 15A shows the color imageprinted on the white soft signage media without any attempt toimmobilize the ink before curing, FIG. 15B shows the color image printedafter spraying the cloth with a wetting composition (as disclosed in WO2005/115089) based on 2% acetic acid and 0.1% wetting agent (BYK 348) intap water, and FIG. 15C shows the color image obtain when using aprocess as presented herein, wherein the first part (the immobilizationpart) is applied concomitantly with the second part (colored part),demonstrating the superb results obtained when using the inkjet printingprocess presented herein.

Since laminated, plasticized and other composite substrates such as softsignage do not suffer from loose and protruding fibers, theimmobilization part of the ink composition can be prepared without theacrylic emulsion binder, as presented in Table 6 below.

TABLE 6 Immobilization Part Lactic acid (property-adjusting agent)   9%Ammonia (for buffering the acid)   3% A mixture of propylene glycol,diethylene glycol   50% and glycerin (as humectants) Benzotriazole (asanti cupper corrosion agent) 0.40% Sodium nitrate (as anti corrosionagent for 0.20% ferrous metals) Deionized water to 100% Viscosity at 34°C. 10 cp pH 4.7 Surface tension 37 N/m

Example 5

The contribution of the immobilization part to the final image qualitywas evaluated by measuring the printed color intensity on white fabric,and comparing the optical density of the resulting color image to thesame design printed without the immobilization part.

Optical density (OD) is a logarithmic scale of relative lightreflectance from a defined surface. Optical density is used in theprinting industry to measure quantities of ink deposits of printedmaterials. Since OD is determined with respect to a reference color, theunits of OD are absolute numbers.

Optical density values were measured using a color analyzing COLOR PRINT415 device BY Shamrock instruments Ltd to analyze the images obtained inExample 2 and 3 described hereinabove.

Table 7 presents optical density values as measured for pure CMYK colorsin a color image printed on a white and a dark fabric at a resolution of545 dpi on a solid fully covered square (100% surface coverage), inthree different printing processes, namely without any attempt toimmobilize the colored part, using a wetting composition (as disclosedin WO 2005/115089) based on 2% acetic acid in tap water, and using animmobilization part applied at 33% of the drop-density of the CMYKcolored part applying a process as described in Example 1 hereinabove.

TABLE 7 Optical density Colored Wetting Immobilization part Noimmobilization composition part On white textile (CMYK at 545 dpi) C1.10 1.27 1.45 M 1.00 1.17 1.14 Y 0.96 1.00 1.45 K 1.17 1.29 1.53 Ondark textile with a white underbase part (CMYK at 545 dpi) C notmeasurable 1.46 1.60 M not measurable 1.22 1.56 Y not measurable 1.101.37 K not measurable 1.41 1.75 Soft signage (CMYK at 454 dpi) C 1.201.62 1.65 M 1.02 1.40 1.50 Y 0.78 0.80 0.80 K 1.21 1.64 1.70

As can be seen in Table 7, the optical density values, which are attheir lowest values on both the untreated fabrics, increases when thefabrics were sprayed with a wetting composition, but afforded theirhighest values when the second (colored) part(s) where appliedconcomitantly with the first (immobilization) part of the inkcomposition, according to the process presented herein.

Example 6

To demonstrate the effect of using proto-elastomeric film-formingingredients in the ink composition, the contribution of the elasticityof the film constituting the finished image printed on a highlystretchable substrate is illustrated.

The proto-elastomeric film-forming acrylic emulsions which are used inthe ink compositions described herein, serve to bestow flexibility andstretchability to the underbase and colored parts of the inks, and moreso with respect to the opaque underbase layer when applied on a dark(black) stretchable garment. If the underbase is not visually continuousat all conformation of the garment, relaxed or stretched, the dark colorof the garment will be partially visible through the image, therebydegrading its appearance and color intensity.

The same requirements of the film are present when the stretchablegarment under the film is lighter in color than the image, namely thestretchability of the image should coincide with the stretchability ofgarment so as not to allow the garment to be seen under the stretchedimage.

Since the stretchability of the underbase part is required, theconcentration of the emulsified proto-elastomeric film-forming agent(acrylic resin) that is used is more then double compared to the amountthereof used in the colored part of the ink.

In order to demonstrate the results of using other multi-part inkcompositions known in the art on stretchable substrate, an identicalimage was printed on an identical highly stretchable black fabricsubstrate (black Lycra™) using identical machinery and process routines.The difference between the images was in the formulation of the opaquewhite underbase part of an ink composition, which was prepared similarlyto that of the opaque white underbase part presented herein, all but tothe different acrylic binder exhibiting a Tg of over 85° C. The coloredand immobilization parts used for all images were identical, except theacrylic binder in the formulation of the opaque white underbase aspresented in Table 3 hereinabove, which was replaced with JONCRYL™acrylate having a high Tg over 20° C.

FIGS. 16A-16B present color photographs of one color image printed on ahighly stretchable black fabric (Lycra™), which was printed using anexemplary ink composition based on proto-elastomeric film-forming agentshaving Tg lower than 0° C., as presently disclosed, and printed using anexemplary process as presently disclosed, wherein FIG. 16A shows theimage on the relaxed fabric which spans about 6 cm, and FIG. 16B showsthe same image in the same piece of fabric, stretched to about 10.5 cmwithout shown any degradation to the image due to stretching.

As can be seen in FIGS. 16A-16B, the colored image appears the same whenthe fabric is relaxed or when it is stretched by about 2-fold of itsrelaxed conformation, demonstrating the successful ink-jet printing of acolored image on a highly stretchable black fabric using the inkcompositions and processes presented herein.

FIGS. 17A-17B present color photographs of two similar color imagesprinted on a highly stretchable black fabric (Lycra™), which wereprinted using an ink composition with film-forming agents having Tghigher than 85° C., and applied using an exemplary process as presentlydisclosed, wherein FIG. 17A shows a similar image as presented in FIG.16 hereinabove on the same type of fabric as shown in FIG. 16, stretchedto about 10.5 cm, showing the cracks and the damaging effect ofstretching the non-elastic image, and FIG. 17B where another image wasprinted with an extended opaque white underbase, showing the cracks andextensive degradation of the image due to stretching, as compared to thestretched image in FIG. 16B.

Example 7

Following are some general ink-part formulations comprising inkcompositions according to embodiments of the present invention, that areimmobilized independently of the dispersed pigments.

Suitable silicon dioxide examples based on treated and untreated fumedsilica (first metal oxide class), are available as AEROSIL® andAERODISP® series from Evonik, or CAB-O-SIL® nano-sized silica seriesfrom the Cabot Corporation.

Nanoparticles of titania are available from Evonik as VP Disp W2730X,740X, VP Titania P90 based on 25 nm titanium dioxide particles.

Alumina nanoparticles are available from Evonik as VP Disp W440W, VPAEROPERL® P25/20, from Cabot Corporation as SPECTR-A1® fumed aluminaseries from BYK chemie, or from Nanophase Technologies Corp.(Romeoville, Ill.) and BYK-Chemie (Wesel, Germany) under the trade namesNANOBYK-3600™ and NANOBYK-3601™.

Formulations of exemplary second parts, containing pre-ground positivelycharged fumed silica particles, such as the commercially availableAERODISP® from Evonik, acting as a first metal oxide to enableimmobilization thereof by an organic acid are presented in Table 8below.

TABLE 8 Fumed silica based second part CMYK ground dispersed pigment10-15% Acrylic low Tg emulsion 10-25% Positively charged fumed silica15-20% Humectants - Glycols 25-40% Wetting agent  0.1-2% Defoamer0.2-0.6%  Bactericide/Fungicide 0.2-0.5%  A crosslinking agent  3-4% Apolymerization catalyst 0.5-0.75%  Deionized water to  100%

Formulations of exemplary second parts, containing nano-sized titaniumdioxide particles, about 25 nm in size such as commercially availablefrom Evonik, incorporated as a first metal oxide to enableimmobilization thereof by an organic acid, are presented in Table 9below.

TABLE 9 Nanoparticle titania based second part CMYK ground dispersedpigment 10-15% Acrylic low Tg emulsion 10-25% Nano titania ~25 nm 15-20%Humectants - Glycols 25-40% Wetting agent  0.1-2% Defoamer 0.2-0.6% Bactericide/Fungicide 0.2-0.5%  A crosslinking agent  3-4% Apolymerization catalyst 0.5-0.75%  Deionized water to  100%

As discussed hereinabove, while the immobilization of the second partrequires a drop of the pH level below 7 in some cases, using alumina asa property-adjusting agent causes instantaneous congelation of thesecond part upon contact regardless any change of the pH level.

The colored part (second part) which is intended for immobilizationeffected by alumina contain only the ink related components, while theimmobilization part contains nano-sized dispersed alumina, as presentedin Table 10 below.

TABLE 10 CMYK inks to be immobilized by alumina CMYK ground dispersedpigment 10-15% Property-sensitive film forming acrylic 10-20% emulsionhaving a low Tg Humectants - Glycols 25-40% Wetting agent  0.1-2%Defoamer 0.2-0.6%  Bactericide/Fungicide 0.2-0.5%  A crosslinking agent 3-4% A polymerization catalyst 0.5-0.75%  Deionized water to  100%

The immobilization part (first part) corresponding to the colored partpresented in Table 10 above, is presented in Table 11 below.

TABLE 11 Alumina based immobilization part Property-adjusting nano-sizedAl₂O3 particles dispersion  10-15% Humectants - Glycols  25-40% Wettingagent  0.1-2% Defoamer 0.2-0.6% Bactericide/Fungicide 0.2-0.5% Deionizedwater to   100%

An exemplary fourth part (“spot colorant” part) which is typically usedto emphasize some areas of the image with brighter opaque colors, ispresented in Table 12 below.

TABLE 12 Opaque colored fourth part AZUL/BLUE ORGAPLAST A-16500/1; or 2-8% MARRON/BROWN INORPINT FeO-300; or NARANJA/ORANGE INORPLASTCD-10807/5; or other commercially available spot colors pigmentsProperty-sensitive film forming acrylic emulsion having a low Tg Tego750 W (dispersant) 0.5-2% BYK 307 (wetting agent) 0.5-2% BYK 017(defomer) 0.5-2% Humectants - Glycols 15-20%  Wetting agent 0.1-2%Defoamer 0.2-0.6%  Bactericide/Fungicide 0.2-0.5%  Deionized water to  100%

Example 8

Following are some general ink compositions, according to someembodiments of the present invention, which comprise formaldehyde-freecrosslinking agents.

Table 13 presents an exemplary second (colored) part of an inkcomposition, using glyoxal, which is completely soluble in water, as anexemplary formaldehyde-free crosslinking agent, according to someembodiments of the present invention.

TABLE 13 Colored (CMYK) part comprising glyoxal A colorant mixture10-20% Property-sensitive proto-elastomeric film forming agent 25-30% Afirst metal oxide (optional if using a third metal oxide) 10-20%Humectants (glycol mixture) 20-40% Glyoxal 40 (as a dialdehydecrosslinking agent)  5-10% Bactericide/Fungicide  0.1-1% Blocked acidcatalyst  0-1.5% Neutralizing/buffering agent 0.2-0.6%  Defoamer 0.10.6%  Wetting agent/surfactant  0.1-2% Organic solvent  0-5% Otheradditives  0-2% Deionized water To   100% Tg of the film-forming agent−35 to 0° C. Viscosity at 34° C. 10-13 cp pH 8-8.5 Surface tension 25-36N/m

Table 14 presents an exemplary third (underbase) part of an inkcomposition, using glyoxal as an exemplary formaldehyde-freecrosslinking agent, according to some embodiments of the presentinvention.

TABLE 14 Opaque white (underbase) part comprising glyoxal A second metaloxide (acting also as colorant) 15-20% Property-sensitiveproto-elastomeric film forming agent 25-45% An optionalproto-elastomeric film forming agent 15-20% Humectants 30-45% Dispersant 1-6% Glyoxal 40 (as a dialdehyde crosslinking agent)  5-10%Bactericide/Fungicide 0.1-0.5%  Blocked acid catalyst  0-1.5%Neutralizing/buffering agent 0.1-0.2%  Defoamer 0.2-0.4%  Wettingagent/surfactant 0.1-0.5%  Organic solvent  0-5% Other additives  0-10%Deionized water To   100% Tg of the film-forming agent −35 to 0° C.Viscosity at 34° C. 12-14 cp pH 8-8.5 Surface tension 25-36 N/m

Table 15 presents an exemplary third (underbase) part of an inkcomposition, using a carbamate-based crosslinking agent as an exemplaryformaldehyde-free crosslinking agent, according to some embodiments ofthe present invention.

As heteroaryl polycarbamate-based crosslinking agents are less insolublein water, but readily dissolve in alcohols and/or glycols, the organicsolvents mixture component of this part of the ink composition has beenadjusted with more polar humectants in order to introduce thecrosslinker into the aqueous media. Otherwise, these formulations arerather similar to formulation presented the former example.

TABLE 15 Opaque white (underbase) part comprising A second metal oxide(acting also as colorant) 15-20% Property-sensitive proto-elastomericfilm forming agent 25-45% An optional proto-elastomeric film formingagent 15-20% Polar humectants (glycerin, propylene glycol, 30-45%monoethylene glycol) Dispersant  1-6% CYLINK ®2000 (as a carbamate-basedcrosslinking agent) 0.5-1.5%  Bactericide/Fungicide 0.1-0.5%  Blockedacid catalyst 0-0.75%  Neutralizing/buffering agent 0.1-0.2%  Defoamer0.2-0.4%  Wetting agent/surfactant 0.1-0.5%  Organic solvent  0-5% Otheradditives  0-10% Deionized water To   100% Tg of the film-forming agent−35 to 0° C. Viscosity at 34° C. 12-14 cp pH 8-8.5 Surface tension 25-36N/m

Table 16 presents an exemplary second (colored) part of an inkcomposition, using diacetone acrylamide (DAAM) and hydrazine as anexemplary formaldehyde-free crosslinking agent, according to someembodiments of the present invention.

The mixture of diacetone acrylamide (DAAM) and hydrazine reacts in situwhen the composition is dried or cured, and serves as crosslinking agentfor acrylic emulsions that serve as a binder to the fabric.

TABLE 16 Colored (CMYK) part comprising DAAM/hydrazine A colorantmixture 10-20% Property-sensitive proto-elastomeric film forming agent25-30% A first metal oxide (optional if using a third metal oxide)10-20% Humectants (glycol mixture) 20-40% DAAM 0.8-1.5%  Hydrazine 0.9-2% Bactericide/Fungicide  0.1-1% Blocked acid catalyst  0-1.5%Neutralizing/buffering agent 0.2-0.6%  Defoamer 0.1-0.6%  Wettingagent/surfactant  0.1-2% Organic solvent  0-5% Other additives  0-2%Deionized water To   100% Tg of the film-forming agent −35 to 0° C.Viscosity at 34° C. 10-13 cp pH 8-8.5 Surface tension 25-36 N/m

Table 17 presents an exemplary third (underbase) part of an inkcomposition, using diacetone acrylamide (DAAM) and hydrazine as anexemplary formaldehyde-free crosslinking agent, according to someembodiments of the present invention.

TABLE 17 Opaque white (underbase) part comprising DAAM/hydrazine Asecond metal oxide (acting also as colorant) 15-20% Property-sensitiveproto-elastomeric film forming 25-45% agent An optionalproto-elastomeric film forming agent 15-20% Humectants 30-45% Dispersant 1-6% DAAM 0.8-1.5%  Hydrazine  0.9-2% Bactericide/Fungicide 0.1-0.5% Blocked acid catalyst  0-1.5% Neutralizing/buffering agent 0.1-0.2% Defoamer 0.2-0.4%  Wetting agent/surfactant 0.1-0.5%  Organic solvent 0-5% Other additives  0-10% Deionized water To   100% Tg of thefilm-forming agent −35 to 0° C. Viscosity at 34° C. 12-14 cp pH 8-8.5Surface tension 25-36 N/m

EXPERIMENTAL CONCLUSIONS

The use of proto-elastomeric film-forming agents to constitute an inkjetformulation, which overcomes smearing, bleeding and wicking, wasdemonstrated herein. The images formed by the compositions and processesdisclosed herein exhibit the highest values of quality criteria, andmaintain these criteria even when the substrate they are printed on aredark and/or highly stretchable.

Methodologies using immobilization compositions to assist in preventingcolored ink compositions from wicking into the substrate have beendescribed in the art. As the immobilization part causes gelation (atleast partial solidification) of the ink composition, any contactbetween the immobilization ink and the color ink will be destructive tothe printheads that are the most sensitive and expensive part of theprinting system.

Practicing the process presented herein has shown that the reservoirs,vacuum generators, tubing and printheads carrying and delivering theimmobilization part of the ink composition must be physically separatedfrom the systems carrying the colored parts of the ink composition so asto prevent any contact therebetween prior to both reaching thesubstrate.

For example, if the property-adjusting agent is highly volatile, it ispractically impossible to control its spread by vapor diffusion overtime. The present inventors have found after numerous trials withdifferent organic acids that lactic is highly suitable due to itstransitoriness and lack of odor.

The immobilization part ingredients must be compatible with theprinthead construction materials, the adhesives ingredients, the ferrousand nonferrous metal conductors and the other electronic components,particularly in cases where the property-adjusting agent is an acid. Inthese cases the pH of the immobilization part must be kept bufferedbetween 4 and 10, and preferably between 4.5 and 8. The organiccomponents must be compatible with epoxy and polyurethane adhesiveswhich are typically used in the makeup of the printing machine, andanti-corrosion agents must be considered in order to protect the metals.

The immobilization part should include component that will stick/attachthe very thin fibers that protrude up to few millimeters over thesurface of textile substrates so as to prevent the fibers fromobstructing the fine jetted drops from reaching the surface of thefabric, and after drying, to prevent the fibers from partly restrictingthe sharpness of the printed image. When printing on non-fibroussubstrates, the immobilization part of the ink composition can be devoidof a binder.

Although the invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives, modificationsand variations will be apparent to those skilled in the art.Accordingly, it is intended to embrace all such alternatives,modifications and variations that fall within the spirit and broad scopeof the appended claims.

It is the intent of the Applicant(s) that all publications, patents andpatent applications referred to in this specification are to beincorporated in their entirety by reference into the specification, asif each individual publication, patent or patent application wasspecifically and individually noted when referenced that it is to beincorporated herein by reference. In addition, citation oridentification of any reference in this application shall not beconstrued as an admission that such reference is available as prior artto the present invention. To the extent that section headings are used,they should not be construed as necessarily limiting. In addition, anypriority document(s) of this application is/are hereby incorporatedherein by reference in its/their entirety.

What is claimed is:
 1. An inkjet composition comprising a film-formingagent or binder, a pigment, and a carrier, the composition ischaracterized by a high pH level greater than 7, wherein the compositioncongeals upon exposure to a low pH level below 7, and forms an elasticfilm upon drying/curing, said film is characterized by highwash-fastness, and an elongation percentage of at least 30%.
 2. Thecomposition of claim 1, wherein said low pH level ranges from 3.5 to5.5.
 3. The composition of claim 1, wherein said film-forming agent orbinder is characterized by a glass transition temperature (Tg) thatranges from −35° C. to 0° C.
 4. The composition of claim 3, wherein saidfilm-forming agent or binder is selected from the group consisting ofnon-ionic water-emulsifiable resin, an acrylic polymer or copolymer, analkyl-acrylic polymer copolymer, an acrylic-styrene copolymer, apolyurethane, a polyether, a polyester, a polyacrylate and antcombination thereof.
 5. The composition of claim 4, wherein saidfilm-forming agent or binder is a self-crosslinking alkyl-acryliccopolymer.
 6. The composition of claim 5, wherein said self-crosslinkingalkyl-acrylic copolymer is a formaldehyde-free crosslinking agent. 7.The composition of claim 5, wherein said self-crosslinking alkyl-acryliccopolymer is an ethyl-acrylic/butyl-acrylic copolymer.
 8. Thecomposition of claim 1, further comprising a crosslinking agent.
 9. Thecomposition of claim 8, wherein said crosslinking agent is aformaldehyde-free crosslinking agent selected from the group consistingof a polyaldehyde, a heteroaryl polycarbamate, a diacetoneacrylamide/hydrazine and a carbodiimide.
 10. A process of digitallyprinting an image on a textile substrate, comprising: applying a wettingcomposition to at least an ink receiving portion of the textilesubstrate to thereby obtain a wet substrate; flattening said wetsubstrate using a flattening unit, inkjet printing the image using theinkjet composition of claim 1 onto said portion, and subsequent to saidinkjet printing, drying/curing said image, thereby forming the image ina form of an elastic film characterized by an elongation percentage ofat least 30%.
 11. The process of claim 10, wherein said wettingcomposition is an aqueous solution that comprises an acid.
 12. Thecomposition of claim 10, wherein said property-adjusting agent is anorganic acid.
 13. The composition of claim 12, wherein said acid is atransitory organic acid.
 14. The composition of claim 13, wherein saidtransitory organic acid is selected from the group consisting of lacticacid, glycolic acid, acetic acid and any combination thereof.
 15. Theprocess of claim 10, wherein said applying is effected by spraying froma nozzle or by inkjet printing from an inkjet printhead.
 16. The processof claim 10, wherein said inkjet printing is effected while said wetsubstrate is still wet from said wetting composition.